記述言語：英語   掲載種別：研究論文（学術雑誌）

Pulsating Aurora (PsA) is one of the major classes of diffuse aurora associated with precipitation of a few to a few tens of keV electrons from the magnetosphere. Recent studies suggested that, during PsA, more energetic (i.e., sub-relativistic/relativistic) electrons precipitate into the ionosphere at the same time. Those electrons are considered to be scattered at the higher latitude part of the magnetosphere by whistler-mode chorus waves propagating away from the magnetic equator. However, there have been no actual cases of simultaneous observations of precipitating electrons causing PsA (PsA electrons) and chorus waves propagating toward higher latitudes; thus, we still do not quite well understand under what conditions PsA electrons become harder and precipitate to lower altitudes. To address this question, we have investigated an extended interval of PsA on 12 January 2021, during which simultaneous observations with the Arase satellite, ground-based all-sky imagers and the European Incoherent SCATter (EISCAT) radar were conducted. We found that, when the PsA shape became patchy, the PsA electron energy increased and Arase detected intense chorus waves at magnetic latitudes above 20°, indicating the propagation of chorus waves up to higher latitudes along the field line. A direct comparison between the irregularities of the magnetospheric electron density and the emission intensity of PsA patches at the footprint of the satellite suggests that the PsA morphology and the energy of PsA electrons are determined by the presence of “magnetospheric density ducts,” which allow chorus waves to travel to higher latitudes and thereby precipitate more energetic electrons.

DOI： 10.1029/2024JA032617

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We made observations of magnetic field variations in association with pulsating auroras with the magneto-impedance sensor magnetometer (MIM) carried by the Loss through Auroral Microburst Pulsations (LAMP) sounding rocket that was launched at 11:27:30 UT on 5 March 2022 from Poker Flat Research Range, Alaska. At an altitude of 200–250 km, MIM detected clear enhancements of the magnetic field by 15–25 nT in both the northward and westward components. From simultaneous observations with the ground all-sky camera, we found that the footprint of LAMP at the 100 km altitude was located near the center of a pulsating auroral patch. The auroral patch had a dimension of ∼90 km in latitude and ∼25 km in longitude, and its major axis was inclined toward northwest. These observations were compared with results of a simple model calculation, in which local electron precipitation into the thin-layer ionosphere causes an elliptical auroral patch. The conductivity within the patch is enhanced in the background electric field and as a result, the magnetic field variations are induced around the auroral patch. The model calculation results can explain the MIM observations if the electric field points toward southeast and one of the model parameters is adjusted. We conclude that the pulsating auroral patch in this event was associated with a one-pair field-aligned current that consists of downward (upward) currents at the poleward (equatorward) edge of the patch. This current structure is maintained even if the auroral patch is latitudinally elongated.

DOI： 10.1029/2023JA032232

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The Van Allen Probes mission contributed to the discovery of the relativistic (∼500 keV–2 MeV) and ultra-relativistic (∼>2 MeV) electron three-belt structure in Earth's radiation belts. This structure results from the partial depletion of the preexisting outer belt and the replenishment of a new outer belt. Ultra-low frequency and very-low frequency waves are believed to play important roles in these processes, and substorm injections are usually not responsible for the formation of the external outer belt. In this study, based on observations from the Arase and NOAA-18 (National Oceanic and Atmospheric Administration-18) satellites, we report an electron three-belt event in the energy range of ∼100–200 keV (i.e., sub-relativistic electrons). According to the evolution of the phase space density and the dawn-dusk asymmetric flux enhancement during this event, we conclude that the depletion of the upper part of the original outer belt was due to outward radial diffusion accompanied by magnetopause shadowing effect and convection, and the formation of the external outer belt was due to increased electron flux from convection as well as substorm injections. This discovery and its preliminary explanation may help understand the electron three-belt structure in radiation belts more comprehensively.

DOI： 10.1029/2023JA032213

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Plasmaspheric hiss waves are important to shape the Earth’s electron radiation belt. These waves are commonly envisioned to have a long lifetime which allows them to permeate the global plasmasphere from a spatially restricted source. However, this hypothesis has not been experimentally confirmed yet, because of the challenging observational requirements in terms of location and timing. With wave and particle measurements from five magnetospheric satellites and detailed modeling, we present the first report of long lifetime (∼42 s) hiss rays in the substorm-disturbed plasmasphere. The low-frequency hiss waves are found to originate from the middle piece of the plasmaspheric plume, bounce between two hemispheres, and eventually drift into the plasmaspheric core. These hiss rays can travel through ∼3 hr magnetic local time and ∼4 magnetic shell. Such a long-time and large-scale permeation of hiss rays could benefit from the ducting process by plasmaspheric field-aligned density irregularities.

DOI： 10.1029/2023GL107825

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

In order to develop practical space human resources on an interdisciplinary of science and engineering fields, Kyushu Institute of Technology and the Kyushu University collaborated to implement a 2U-size CubeSat development program for undergraduate students. In this program, students from different universities and different disciplines work together to develop satellites to accomplish full-scale scientific missions. To guide this program, complementary educational programs in science and engineering were established, and the two universities collaborated to educate the students. In this paper we report the outline and implementation of this initiative.

DOI： 10.52202/078378-0164

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have identified for the first time an energy-time dispersion of precipitating electron flux in a pulsating aurora patch, ranging from 6.7 to 580 keV, through simultaneous in-situ observations of sub-relativistic electrons of microburst precipitations and lower-energy electrons using the Loss through Auroral Microburst Pulsation sounding rocket launched from the Poker Flat Research Range in Alaska. Our observations reveal that precipitating electrons with energies of 180–320 keV were observed first, followed by 250–580 keV electrons 0–30 ms later, and finally, after 500–1,000 ms, 6.7–14.6 keV electrons were observed. The identified energy-time dispersion is consistent with the theoretical estimation that the relativistic electron microbursts are a high-energy tail of pulsating aurora electrons, which are caused by chorus waves propagating along the field line.

DOI： 10.1029/2023GL104001

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

A specialized ground-based system has been developed for simultaneous observations of pulsating aurora (PsA) and related magnetospheric phenomena with the Arase satellite. The instrument suite is composed of (a) six 100 Hz sampling high-speed all-sky imagers (ASIs), (b) two 10 Hz sampling monochromatic ASIs observing 427.8 and 844.6 nm auroral emissions, (c) a 20 Hz sampling fluxgate magnetometer. The 100 Hz ASIs were deployed in four stations in Scandinavia and two stations in Alaska, which have been used for capturing the main pulsations and quasi 3 Hz internal modulations of PsA at the same time. The 10 Hz sampling monochromatic ASIs have been operative in Tromsø, Norway with the 20 Hz sampling magnetometer. Combination of these multiple instruments with the European Incoherent SCATter (EISCAT) radar enables us to detect the low-altitude ionization due to energetic electron precipitation during PsA and further to reveal the ionospheric electrodynamics behind PsA. Since the launch of the Arase satellite, the data from these instruments have been examined in comparison with the wave and particle data from the satellite in the magnetosphere. In the future, the system can be utilized not only for studies of PsA but also for other classes of aurora in close collaboration with the planned EISCAT_3D project.

DOI： 10.1029/2023JA031527

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Magnetometers are important sensors with applications in the attitude determination and control systems of satellites. CubeSats have certain limitations related to power, mass, and volume. Due to this, CubeSat magnetometers are not separated from other electrical circuits inside the satellite. Thus, it is important to calibrate the magnetometer, simulating operating conditions while the satellite is running before the launch. However, due to the limited facilities, not every CubeSat is able to calibrate its magnetometers properly on the ground. This study focuses on the calibration of on-orbit magnetometer data observed by BIRDS-3 CubeSats with a genetic algorithm. High oscillations in the total magnetic field were found in the on-orbit magnetic field data measured by magnetometers inside BIRDS-3 CubeSats. Nine unknowns, scaling factors, non-orthogonal angles, and offsets are identified with the genetic algorithm. This paper discusses the factors that affect the high oscillations in the measured total magnetic field data. For the calibration, we used magnetic field data similar to those of a model magnetic field, as the deviation is smaller. This paper presents the accuracy of determining unknowns using the genetic algorithm, as well as the interchangeability of the answers with additional orbit data from the same satellite. This method can be used in the future to calibrate magnetometers inside CubeSats before or after launch.

DOI： 10.3390/app13116742

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Because of its communication volume constraints, scientific observations by nanosatellites need to reduce downlink data by onboard data preprocessing. Therefore, we tried to classify time series data of the geomagnetic field obtained by the SWARM satellite to determine the most appropriate method for onboard classification of a phenomenon in the geomagnetic field. The classifications have been executed using rule-based, K-means, and combined CNN methods. The experimental results demonstrated the effectiveness of the machine-learning model with LSTM networks.

DOI： 10.5954/icarob.2023.gs1-3

CiNii Research

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

This paper focuses on the analysis of the magnetic field measurements observed by the nanosatellite KITSUNE, focusing on the calibration methods used during the development and operations of the satellite. KITSUNE is a 6U CubeSat developed at Kyushu Institute of Technology, Japan, and deployed to orbit on 24th March 2022. It is equipped with an active 3-axis attitude control system consisting of reaction wheels, magnetorquers, an Inertial Measurement Unit (IMU), an external magnetometer, and six coarse sun sensors. Typically, the magnetometers used in CubeSats missions are attached to the satellite body. Hence, the magnetometers can give unexpected results due to scaling factors, offsets, and non-orthogonality errors. The non-orthogonality errors are defined as angular deviations from the orthogonal three-axis. The genetic algorithm is being used in this study to calibrate the on-orbit magnetometer data. As a study case, the on-orbit magnetic field data collected by this magnetometer was used to demonstrate the performance of the proposed genetic algorithm to calibrate the magnetometer on the ground. The Fortran language is used to develop the genetic algorithm to calibrate the magnetometer data. The genetic algorithm uses a weight function to find the best match for the unknowns. A relationship between the reference magnetic field, the measured magnetic field by the magnetometer, offsets, and scaling factors, is used as the weight function of this study. The magnetometer data from the International Geomagnetic Reference Field (IGRF) is used as the reference magnetic field in the weight function. The results of the implemented genetic algorithm for the calibration of KITSUNE magnetometer show that the observed error in the measured magnetic field can be reduced by this method.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

The BIRDS program started in 2015 at Kyushu Institute of Technology where young professionals from non-space-faring countries join satellite projects as graduate course students and develop 1U CubeSat with Japanese students. In July 2020, the BIRDS-5 project, the fifth generation of the BIRDS program, began with students from Uganda, Zimbabwe, and Japan. BIRDS-5 project built one 1U CubeSat each for Uganda and Zimbabwe and one 2U CubeSat for Japan in around two years. The BIRDS-5 project applied the Lessons Learned from BIRDS-1, -2, -3, and -4, and improved technology and management points to reduce the development time and cost and avoid making the same mistakes as previous projects. The three satellites were released from the International Space Station (ISS) in December 2022. However, no signals were received from all three satellites since their deployment. The BIRDS-5 team performed Fault Tree Analysis (FTA) for possible causes. Extensive tests were performed using the back-up satellite to replicate the phenomena in orbit. Tests were repeated to deny any unnoticed issues during the satellite development. This paper describes the improvements made by the BIRDS-5 project based on the heritage from the previous projects and summarizes the unpredicted issues that appeared in the BIRDS-5 project. In addition, the results of the failure investigation and suggestions to prevent future projects from making the same failures are also detailed. This study will be beneficial for all the small satellite developers as lessons learned while developing satellites using commercial-off-the-shelf components in a limited time.

Scopus

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記述言語：日本語   掲載種別：研究論文（学術雑誌）

レポート番号: S2-004

CiNii Research

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Because of its communication volume constraints, scientific observations by nanosatellites need to reduce downlink data by onboard data preprocessing. Therefore, we tried to classify time series data of the geomagnetic field obtained by the SWARM satellite to determine the most appropriate method for onboard classification of a phenomenon in the geomagnetic field. The classifications have been executed using rule-based, K-means, and combined CNN methods. The experimental results demonstrated the effectiveness of the machine-learning model with LSTM networks.

Scopus

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Inner magnetospheric electrons are precipitated in the ionosphere via pitch-angle (PA) scattering by lower band chorus (LBC), upper band chorus (UBC), and electrostatic electron cyclotron harmonic (ECH) waves. However, the PA scattering efficiency of low-energy electrons (0.1–10 keV) has not been investigated via in situ observations because of difficulties in flux measurements within loss cones at the magnetosphere. In this study, we demonstrate that LBC, UBC, and ECH waves contribute to PA scattering of electrons at different energy ranges using the Arase (ERG) satellite observation data and successively detected the moderate loss cone filling, that is, approaching strong diffusion. Approaching strong diffusion by LBC, UBC, and ECH waves occurred at ∼2–20 keV, ∼1–10 keV, and ∼0.1–2 keV, respectively. The occurrence rate of the approaching strong diffusion by high-amplitude LBC (>50 pT), UBC (>20 pT), and ECH (>10 mV/m) waves, respectively, reached ∼70%, ∼40%, and ∼30% higher than that without simultaneous wave activity. The energy range in which the occurrence rate was high agreed with the range where the PA diffusion rate of each wave exceeded the strong diffusion level based on the quasilinear theory.

DOI： 10.1029/2022JA030269

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Flux enhancements of field-aligned low-energy O+ ion (FALEO) are simultaneously observed by Arase, Van Allen Probes A and B in the nightside inner magnetosphere during 05–07 UT on September 22, 2018. FALEOs appear after a magnetic dipolarization signature with approximately 6–20 min delay. It has the energy-dispersion signature from a few keV to ∼100 eV only in the direction parallel to the magnetic field at Arase, while it decreases its energy from a few keV down to 10 eV in both the parallel and antiparallel directions at Probes A and B. We perform a numerical simulation to trace trajectories of test O+ ions in a model magnetosphere, which are launched from above the ionosphere 3–15 min after a substorm. Flying virtual satellites that have the same orbits as the real satellites, we create virtual energy-time spectrograms of O+ ions to compare with the observed ones. Results show a very good correspondence between them, indicating that FALEOs originate from ionospheric O+ ions that are extracted from the upper ionosphere at substorm onset and flow along the magnetic field toward the geomagnetic equator. It is also revealed that 3–9 hr after their launch, test O+ ions less than 400 eV have a spatial distribution in the inner magnetosphere which is similar to those of the warm plasma cloak and the oxygen torus. We therefore conclude that FALEO is a source of those cold ion populations.

DOI： 10.1029/2021JA030008

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Using magnetic field and electron density data from the Arase satellite for the period from March 2017 to September 2019, we investigate the spatial properties of Pi2 pulsations in relation to the plasmapause over a wide latitudinal range (absolute magnetic latitude, |Mlat|, < 45°) in the inner magnetosphere. Magnetic field disturbances that have high coherence (> 0.7) with Pi2 pulsations in the north-south (H) component at low-latitude ground stations on the nightside, are dominantly identified from the magnetic fields in the radial (BR) and compressional (BP) components when the satellite is in the pre-midnight sector. In particular, high-coherence BP events are distributed over wide L-values and latitudinal ranges on the nightside in the pre-midnight sector. We identify the location of the plasmapause using the electron densities measured by Arase, and found that the BP-H power ratio and the cross phases of the high-coherence events show a gradual peak and a clear phase change from 0° to 180° in the vicinity of the plasmapause, respectively. These features indicate that mid- and low-latitude Pi2 pulsations on the nightside are excited by the plasmaspheric virtual resonance mode.

DOI： 10.1029/2021JA029677

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Toroidal standing Alfvén wave is one of the ultra-low frequency waves that are frequently observed in the terrestrial magnetosphere. They sometimes exhibit multi-harmonic frequency spectra, indicating wide energy range input in the magnetosphere. However, their energy source has not been fully understood due to the lack of statistical studies. Here we used the data of the Arase satellite observations for ∼3.5 years and conducted a statistical analysis of the solar wind dependence of the occurrence rate, wave power, and frequency of the multi-harmonic toroidal waves. We automatically detected the multi-harmonic waves and categorized them into four groups according to the solar wind velocity and the cone angle of the interplanetary magnetic field. We found that the occurrence rate and wave power of the multi-harmonic waves increase with the solar wind velocity on the flank sides. In the noon sector, the occurrence rate of the multi-harmonic waves increases with the decrease of the cone angle. The median frequency of the multi-harmonic waves on the dayside is positively correlated with the upstream wave frequency predicted by the theory of the ion beam instability for a small cone angle. The occurrence rate also increases with the solar wind dynamic pressure fluctuations. Therefore, we suggest that the Kelvin-Helmholtz instability, the upstream waves, and the dynamic pressure fluctuations are possible sources of the multi-harmonic waves. This study sheds light on the activity of the multi-harmonic waves which can affect radiation belt electrons under various solar wind conditions.

DOI： 10.1029/2021JA029840

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Japan Aerospace Exploration Agency researches the technology for active space debris removal. The anti-charging measure at the moment of capture operation is one of research topics. In order to consider effective countermeasure, we need to know how much potential difference can be possible. As is well known, the charged particles that cause satellite charging depends on the type of orbit. We investigate the potential difference in the polar orbit, which is known as congested orbit populated by many space debris. Through this investigation, we expect to clarify the relationship between plasma environment and potential difference at capture operation. We utilize the past observation results by the DMSP satellites for the plasma environment conditions. We change the ionospheric plasma density from the order of 108/m3 to 1010/m3, and the current density of auroral electron from 1×10-4A/m to 1×10-6A/m. The other environmental parameters are shown in the presentation. We use Multi-Utility Spacecraft Charging Analysis Tool, MUSCAT to obtain the potential difference between the debris and the satellite. MUSCAT is a 3D charging simulation tool. We make the grid models of the satellite and the upper stage of H-II A rocket which is assumed as the removal target in the analysis domain. Whether the potential difference was safe or not was determined based on the Japanese spacecraft charging design guideline. The simulation result shows that if the plasma density is of the order of 1010/m3, the potential difference is low enough to ignore the risk of discharge. If the plasma density is lower than 1010/m3, the auroral electron current density is the dominant parameter for the potential difference. Since the risk of discharge depends on the plasma density, a device to measure the plasma density is necessary for a debris removal satellite.

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Satellite signal delays and errors depend on the amount of ionosphere Total Electron Content (TEC) in the signal path. The measurement of TEC has been mostly done using Global Navigation Satellite System (GNSS) signals. Signals from a satellite orbiting in lower altitude with lower frequencies than GNSS may provide more precise measurement of Total Electron Content (TEC). Space Precision Atomic Clock Timing Utility Mission (SPATIUM) is a program to do three-dimensional ionosphere mapping by a satellite constellation in Low Earth Orbit (LEO) measuring TEC with Ultra High Frequency (UHF) radio signals. The first technology demonstration satellite called SPATIUM-I, a 2U CubeSat, was deployed from the International Space Station in October 2018. The satellite emits a 467-MHz reference signal generated by a chip scale atomic clock. The signal is Spread Spectrum (SS)-modulated with 250 chips in 4 ms. This paper explains the methodologies and their results of detecting the signal time delay on the ground using a Software-Defined Radio (SDR). To improve the precision, a Global Positioning System (GPS) clock was used to put a time stamp on the satellite signal every 1 s. The time difference of two consecutive signals is the key method for deriving the TEC difference between two signal paths.

DOI： 10.15866/irease.v15i1.21136

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

This paper discusses the development and instrumentation of an integrated facility based on an air-bearing table to test small ADCS actuators such as electric propulsion devices, reaction wheels, and magnetic torquers for CubeSats. It includes an automatic balancing system that corrects the center of mass of the testing platform and a Helmholtz cage for the simulation of the in-orbit geomagnetic environment inside the vacuum environment. Through experimental tests, it was observed that the attitude disturbances due to the aerodynamic drag and the viscous rotational friction in atmospheric conditions (~5×10-6 Nm) can be significantly decreased when the testing platform is placed inside a vacuum environment (~5×10-7 Nm). It was also observed that the vacuum condition facilitates the verification test of attitude control maneuvers using small magnetic torquers for CubeSats whose control torque is smaller than the attitude disturbance torque in atmospheric conditions. A demonstration test was performed to verify the attitude stabilization control by the magnetic torquers in vacuum conditions under a simulated geomagnetic field as in the International Space Station orbit using this integrated testing facility.

DOI： 10.15866/irease.v15i1.21180

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Using a novel wave-particle interaction analysis, we show observational evidence of energy transfer from fast magnetosonic waves (MSWs) to low-energy protons in the magnetosphere. The analysis clearly indicates that the transferred proton energies are further converted to excite electromagnetic ion cyclotron waves. Since MSWs are excited by hot ions, cross-energy coupling of ions occurs through MSWs. The result also suggests a new energy transfer path of exciting electromagnetic ion cyclotron waves in the magnetosphere, and a complex interplay between various wave modes and particle populations.

DOI： 10.1103/PhysRevLett.127.245101

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We examined the growth and propagation of fine-structured electromagnetic ion cyclotron (EMIC) waves related to time-varying density irregularities using multipoint measurement data observed by Arase, Van Allen Probe A, and two ground-based induction magnetometers (Gakona and Dawson) during a field line conjunction event on April 18, 2019. We analyzed the wave data obtained by the aforementioned spacecraft and stations, and found that the appearance of fine structures in the observed EMIC waves clearly coincided with the ambient electron density irregularities in the magnetosphere, which can cause periodic wave growth and waveguiding on their propagation. Furthermore, we found that the latitudinal widths of the EMIC wave activity region and the wave propagation duct were ∼185 km and less than 80 km at an auroral altitude of 100 km, respectively. We also found thermal ion heating ((Formula presented.) eV/q) during the EMIC wave activity.

DOI： 10.1029/2021GL096488

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Using Exploration of energization and Radiation in Geospace (ERG or Arase) spacecraft data, we studied low-frequency magnetic field and energetic particle flux oscillations and high-frequency waves deep in the inner magnetosphere at a radial distance of ~4–5 (Formula presented.) during substorm dipolarization. The magnetic field oscillated alternately between dipole-like and taillike configuration at a period of (Formula presented.) 1 min during dipolarization. When the magnetic field was dipole-like, the parallel magnetic component of the Pi2 waves was at trough. Both energetic ion and electron fluxes with a few to tens of kiloelectronvolts enhanced out of phase, indicating that magnetosonic waves were in slow mode. Field-aligned currents also oscillated. These observations are consistent with signatures of ballooning instability. In addition, we found that broadband waves from the Pi1 range to above the electron cyclotron frequency tended to appear intermittently in the central plasma sheet near dipole-like configuration.

DOI： 10.1029/2020JA029095

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The present study examines the low-energy ion flux variations observed by the Arase satellite in the inner magnetosphere. From the magnetic field and ion flux data obtained by the fluxgate magnetometer and the low-energy particle experiments–ion mass analyzer onboard Arase, we find 55 events of the low-energy O+ flux enhancement accompanied with magnetic field dipolarization in the periods of April 1–October 31, 2017 and July 1, 2018–January 31, 2019. The low-energy O+ flux enhancements (a) start a few minutes after the dipolarization onset, (b) have energy-dispersed signatures with decreasing energy from a few keV down to ∼10 eV, (c) are observed in both storm and non-storm periods, (d) have a field-aligned distribution (α ∼ 0° in the southern hemisphere and α ∼ 180° in the northern hemisphere), (e) are accompanied by the low-energy H+ flux enhancements that have lower energies than O+ by a factor of 3–10, and (f) increase the O+ density and the O+/H+ density ratio by ∼10 times and 4–5 times, respectively. We perform a numerical simulation to trace ion trajectories forward in time from the Arase positions. It is revealed that both H+ and O+ ions drift eastward and reach the dawn-to-morning sector without being lost in the ionosphere, if the pitch angle scattering effect is considered near the equatorial plane. This result suggests that these low-energy field-aligned ions can contribute to formation of the warm plasma cloak.

DOI： 10.1029/2021JA029168

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記述言語：英語   掲載種別：研究論文（学術雑誌）

This study reports a relation between electron flux modulations and chorus emissions by using correlation analysis. On April 18, 2017, Arase observed an enhancement of electron fluxes and intensification of banded chorus emissions at the same time. A result of the analysis shows that both the upper-band and lower-band chorus emissions have good correlations with field-aligned electron fluxes that satisfy their resonance conditions. This indicates simultaneous interactions with both the emission bands and electrons, resulting in electron pitch-angle scattering toward the magnetic field direction. In addition, low-energy electron fluxes in the perpendicular direction also show positive correlations with the chorus intensities, probably because the chorus emissions are modulated by a fluctuation of perpendicular low-energy electron fluxes.

DOI： 10.1029/2021GL093708

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Pulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a PsA associated with a weak geomagnetic storm. Simultaneously, the Arase spacecraft has observed intense whistler-mode chorus waves at the conjugate location along magnetic field lines. A computer simulation based on the EISCAT observations shows immediate catalytic ozone depletion at the mesospheric altitudes. Since PsA occurs frequently, often in daily basis, and extends its impact over large MLT areas, we anticipate that the PsA possesses a significant forcing to the mesospheric ozone chemistry in high latitudes through high energy electron precipitations. Therefore, the generation of PsA results in the depletion of mesospheric ozone through high-energy electron precipitations caused by whistler-mode chorus waves, which are similar to the well-known effect due to solar energetic protons triggered by solar flares.

DOI： 10.1038/s41598-021-92611-3

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The Magnetospheric Multiscale (MMS) spacecraft observed many enhancements of electromagnetic ion cyclotron (EMIC) waves in an event in the late afternoon outer magnetosphere. These enhancements occurred mainly in the troughs of magnetic field intensity associated with a compressional ultralow frequency (ULF) wave. The ULF wave had a period of ∼2–5 min (Pc5 frequency range) and was almost static in the plasma rest frame. The magnetic and ion pressures were in antiphase. They are consistent with mirror-mode type structures. We apply the Wave-Particle Interaction Analyzer method, which can quantitatively investigate the energy transfer between hot anisotropic protons and EMIC waves, to burst-mode data obtained by the four MMS spacecraft. The energy transfer near the cyclotron resonance velocity was identified in the vicinity of the center of troughs of magnetic field intensity, which corresponds to the maxima of ion pressure in the compressional ULF wave. This result is consistent with the idea that the EMIC wave generation is modulated by ULF waves, and preferential locations for the cyclotron resonant energy transfer are the troughs of magnetic field intensity. In these troughs, relatively low resonance velocity due to the lower magnetic field intensity and the enhanced hot proton flux likely contribute to the enhanced energy transfer from hot protons to the EMIC waves by cyclotron resonance. Due to the compressional ULF wave, regions of the cyclotron resonant energy transfer can be narrow (only a few times of the gyroradii of hot resonant protons) in magnetic local time.

DOI： 10.1029/2020JA028912

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2021. American Geophysical Union. All Rights Reserved. This report describes electron beams observed at high latitudes in the magnetosphere by the Arase satellite. According to fine angular channel measurements, beam electrons are mainly flowing away from the Earth, and are well collimated to within a few degrees. A statistical study indicates that the beams are seen when Arase is located at Lm > ∼5, and more frequently as the magnetosphere becomes active. The field lines of the beam events are traced back to the typical auroral ovals. The statistical properties of the beams are consistent with the interpretation that ionospheric electrons are accelerated by a parallel electric field of an auroral potential structure and are streaming upward to the high latitude magnetosphere.

DOI： 10.1029/2020GL090522

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2021. American Geophysical Union. All Rights Reserved. We report the properties of the ionospheric exit point and characteristics of several types of very low frequency waves, including chorus and quasiperiodic emissions, based on a comprehensive dataset of simultaneous observations between ground and space. Whistler-mode waves were observed at Kannuslehto (L = 5.5, KAN), Finland, and in the inner magnetosphere by the Japanese Arase satellite. During the 2017–2018 winter campaign, we found 13 cases showing one-to-one correspondence of wave spectra between KAN and Arase. This is the first time that such a large number of conjugated events have been reported at once. The duration of the events ranged from a few minutes up to 3 h, with 90% of events detected in the afternoon sector. While the occurrence rate is higher during daytime, this can also be related to a majority of the detected waves being quasiperiodic emissions, a known dayside phenomenon. Arase was usually located within 30° of the equator, at L ∼4–5, and detected mostly waves propagating at oblique angles (≥20°). Frequently, the ionospheric magnetic footprint of Arase was located equatorwards (south) from KAN, often in the same geographical area. We investigated the probable location of the ionospheric exit point of the waves from the location of the footprint of Arase and the angle of arrival of waves detected at KAN. Using density measurements at Arase we discuss magnetospheric wave propagation; we find that, in most cases, waves were unducted in their propagation from the satellite to the ground.

DOI： 10.1029/2020JA028682

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記述言語：英語   掲載種別：研究論文（学術雑誌）

明滅オーロラとともに起こるオゾン破壊 --宇宙からの高エネルギー電子が大気に及ぼす影響を実証--. 京都大学プレスリリース. 2021-07-14.

CiNii Article

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

There are many satellites and simulation models for measuring ionospheric plasma density; however, there is currently no global 3-dimensional ionospheric map that can capture the time fluctuation of the ionosphere. The SPATIUM project (developed by Kyushu Institute of Technology and Nanyang Technological University) aims at 3- dimensional mapping of the ionosphere using a CubeSat constellation. The project objective is to elucidate the dynamic interaction of the atmosphere, ionosphere, and magnetosphere. This paper describes the system developed for measurement of the total electron content (TEC) of the ionosphere using the SPATIUM-II satellite, which is the second generation of the SPATIUM project. SPATIUM-II occupies 1U of volume and performs the onboard processing of the ranging signal from the ground station (GS) using Chip-Scale Atomic Clock (CSAC), GPS receiver, software defined radio (SDR) and Raspberry Pi (RPi) for measurement of TEC. The electrons of the ionosphere result in radio wave propagation time delay. The propagation time of ranging signal is proportional to TEC. CSAC is used as a precise clock. CSAC and GPS receivers are installed in both the GS and the SPATIUM-II satellite. The 1- PPS (one pulse per second) signal of GPS receiver is used for timing synchronization and measurement of the propagation time delay of ranging signal. The ranging signals are time-synchronized by RF switch and 1-PPS signal, and then received by SDR. The signal is A/D-converted by SDR and transferred to RPi as a digital signal. This digital signal is processed in the RPi for measurement of the TEC. This TEC measurement system has been successfully developed and verified by ground tests. The flight model is complete and ready for delivery. It is scheduled to be launched in late 2021 or early 2022.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2020. American Geophysical Union. All Rights Reserved. Electrostatic electron cyclotron harmonic (ECH) waves are generally excited in the magnetic equator region, in the sector from nightside to dayside during geomagnetically active conditions, and cause the pitch angle scattering by cyclotron resonance. The scattered electrons precipitate into the Earth's atmosphere and cause auroral emission. However, there is no observational evidence that ECH waves actually scatter electrons into the loss cone in the magnetosphere. In this study, from simultaneous wave and particle observation data obtained by the Arase satellite equipped with a high-pitch angular resolution electron analyzer, we present evidence that the ECH wave intensity near the magnetic equator is correlated with an electron flux inside the loss cone with an energy of about 5 keV. The simulation suggests that this electron flux contributes to the auroral emission at 557.7 nm with an intensity of about 200 R.

DOI： 10.1029/2020GL089926

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1029/2020SW002611

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1029/2020JA028765

記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2021, The Author(s). Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite thermosphere atoms to higher energy states at altitude of ~ 100 km; relaxation from these states produces the auroral light. The electric potential accelerating the aurora-producing electrons has been reported to lie immediately above the ionosphere, at a few altitudes of thousand kilometres1. However, the highest altitude at which the precipitating electron is accelerated by the parallel potential drop is still unclear. Here, we show that active auroral arcs are powered by electrons accelerated at altitudes reaching greater than 30,000 km. We employ high-angular resolution electron observations achieved by the Arase satellite in the magnetosphere and optical observations of the aurora from a ground-based all-sky imager. Our observations of electron properties and dynamics resemble those of electron potential acceleration reported from low-altitude satellites except that the acceleration region is much higher than previously assumed. This shows that the dominant auroral acceleration region can extend far above a few thousand kilometres, well within the magnetospheric plasma proper, suggesting formation of the acceleration region by some unknown magnetospheric mechanisms.

DOI： 10.1038/s41598-020-79665-5

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.23919/URSIRSB.2020.9240099

記述言語：英語   掲載種別：研究論文（学術雑誌）

©2020. American Geophysical Union. All Rights Reserved. Various subauroral optical features have been studied by analyzing data collected during periods of geomagnetic disturbances. Most events have been typically found at geomagnetic latitudes of 45–60°. In this study, however, we present a red arc event found at geomagnetic 68° north (L ≈ 7.1) in the Scandinavian sector during a period of geomagnetically quiet conditions within a short intermission between two high-speed solar wind events. The red arc appeared to coincide with a pseudo breakup at geomagnetic 71–72°N and a rapid equatorward expansion of the polar cap. However, the red arc disappeared in approximately 7 min. Simultaneous measurements with the Swarm A/C satellites indicated the appearance of the red arc at the ionospheric trough minimum and a conspicuous enhancement of the electron temperature, suggesting the generation of the arc by heat flux. Since there are meaningful differences in the red arc features from already-known subauroral optical features such as the stable auroral red (SAR) arc, we considered that the red arc is a new phenomenon. We suggest that the ephemeral red arc may represent the moment of SAR arc birth associated with substorm particle injection, which is generally masked by bright dynamic aurorae.

DOI： 10.1029/2020JA028468

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2020. American Geophysical Union. All Rights Reserved. Recent availability of a considerable amount of satellite and ground-based data has allowed us to analyze rare conjugated events where extremely low and very low frequency waves from the same source region are observed in different locations. Here, we report a quasiperiodic (QP) emission, showing one-to-one correspondence, observed by three satellites in space (Arase and the Van Allen Probes) and a ground station. The main event was on 29 November 2018 from 12:06 to 13:08 UT during geomagnetically quiet times. Using the position of the satellites we estimated the spatial extent of the area where the one-to-one correspondence is observed. We found this to be up to 1.21 Earth's radii by 2.26 hr MLT, in radial and longitudinal directions, respectively. Using simple ray tracing calculations, we discuss the probable source location of these waves. At ∼12:20 UT, changes in the frequency sweep rate of the QP elements are observed at all locations associated with magnetic disturbances. We also discuss temporal changes of the spectral shape of QP observed simultaneously in space and on the ground, suggesting the changes are related to properties of the source mechanisms of the waves. This could be linked to two separate sources or a larger source region with different source intensities (i.e., electron flux). At frequencies below the low hybrid resonance, waves can experience attenuation and/or reflection in the magnetosphere. This could explain the sudden end of the observations at the spacecraft, which are moving away from the area where waves can propagate.

DOI： 10.1029/2020JA028126

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2020, The Author(s). We investigate the longitudinal structure of the oxygen torus in the inner magnetosphere for a specific event found on 12 September 2017, using simultaneous observations from the Van Allen Probe B and Arase satellites. It is found that Probe B observed a clear enhancement in the average plasma mass (M) up to 3–4 amu at L = 3.3–3.6 and magnetic local time (MLT) = 9.0 h. In the afternoon sector at MLT ~ 16.0 h, both Probe B and Arase found no clear enhancements in M. This result suggests that the oxygen torus does not extend over all MLT but is skewed toward the dawn. Since a similar result has been reported for another event of the oxygen torus in a previous study, a crescent-shaped torus or a pinched torus centered around dawn may be a general feature of the O+ density enhancement in the inner magnetosphere. We newly find that an electromagnetic ion cyclotron (EMIC) wave in the H+ band appeared coincidently with the oxygen torus. From the lower cutoff frequency of the EMIC wave, the ion composition of the oxygen torus is estimated to be 80.6% H+, 3.4% He+, and 16.0% O+. According to the linearized dispersion relation for EMIC waves, both He+ and O+ ions inhibit EMIC wave growth and the stabilizing effect is stronger for He+ than O+. Therefore, when the H+ fraction or M is constant, the denser O+ ions are naturally accompanied by the more tenuous He+ ions, resulting in a weaker stabilizing effect (i.e., larger growth rate). From the Probe B observations, we find that the growth rate becomes larger in the oxygen torus than in the adjacent regions in the plasma trough and the plasmasphere.[Figure not available: see fulltext.]

DOI： 10.1186/s40623-020-01235-w

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2019. American Geophysical Union. All Rights Reserved. We compare for the first time two conjugate events showing simultaneous very low frequency (VLF) wave observations between the same ground station and spacecraft, at different geomagnetic conditions and on opposite sides of the magnetosphere. Waves were observed at Kannuslehto (MLAT = 64.4°N, L=5.46), Finland, and on board Arase (Exploration of energization and Radiation in Geospace, ERG) in the inner magnetosphere. Case 1 on 28 March 2017 shows quasiperiodic (QP) emissions and chorus simultaneously observed on the postmidnight side during the recovery phase of a storm, with sustained high solar wind speed and AE index. Case 2 on 30 November 2017 shows clear one-to-one correspondence of QP elements on the noonside during geomagnetic quiet time (Dst>10 nT and AE<100 nT). We present the characteristics of both cases, focusing on coherence and spatial extent of the waves, electron density, and magnetic field variations. We report that the magnetic field gradient plays a role in the changes of spectral features of the waves.

DOI： 10.1029/2019JA026663

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Interaction with the solar wind and UV/X-ray irradiation can cause the lunar dust to be electrostatically charged and mobilized all around the Moon, and light scattering by this dust cloud can be observed over the lunar terminator. This phenomenon, which has also been called the lunar horizon glow (LHG), still remains unexplained. The LHG observations using conventional lunar probes have limited observation opportunities and do not cover varying space weather conditions in cislunar environment such as strong upstream plasma flow and micrometeoroid flux that could enhance the lunar dust presence in the exosphere. The nanosatellite “HORYU-6” specialized in LHG observations will be put into lunar orbit to detect the light scattering above the lunar terminator. The proposed payload will perform multi-spectral imaging to monitor the lunar horizon several minutes before orbital sunrise or after orbital sunset for light scattering analysis. We show that we can obtain scientific results of lunar and planetary exploration using CubeSat at low cost and in a short period of time, and contribute to the development of lunar and planetary exploration in the future. The spacecraft will be developed jointly with universities in Singapore, the United States and Italy under the supervision of Kyushu Institute of Technology, with the aim of launching the SLS-2 rocket in the second half of 2022. Together with its own scientific objectives, the HORYU-6 mission will demonstrate the low thrust trajectory optimization by utilizing electric propulsion system together with other novel embedded technology demonstrations such as atomic clock, deep space navigation and communication with CubeSats.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

The ionosphere, which is the upper ionized layer of the atmosphere, affects the transmission of radio waves and causes degradation in the performance of satellite-based navigation, communication, and surveillance systems. Measurements by satellites are used to validate the numerical models of the ionosphere by estimating the total electron content (TEC) along the propagation path of the radio waves from satellite to ground. TEC is simply the total number of electrons along a ray path from a transmitter to the receiver. The delay experienced by a signal travelling in the ionosphere is proportional to the TEC along the signal path. Consequently, mapping the state of the ionosphere in real-time is an important scientific study for the dynamic nature of the ionosphere which would as well help in maintaining the accuracy of these radio-based systems. Various techniques to mitigate these ionospheric effects were developed in the past decades; a widely distributed network of global navigation satellite system (GNSS) receivers provides 3D distributions of the electron density in the ionosphere on the regional scales and its temporal fluctuations. A constellation of CubeSats can be used to estimate TEC along the UHF links between these satellites and a network of ground stations; the time delay of the propagating signals is used to derive a single value of TEC and hence multiple measurements of vertical and slant TEC can be used to derive a global map of the ionosphere. The advantage of using the UHF band is its higher vulnerability to ionospheric effects. This paper will propose the design requirements and hardware implementation and testing of a payload for a CubeSat used for signal timestamped reception using the UHF communication band in addition to on-board processing to derive TEC values between satellite and ground station. The development of this payload is part of Space Precision Atomic-clock TIming Utility Mission (SPATIUM) project which was proposed by Laboratory of Lean Satellite Enterprises and In-Orbit Experiments (LaSEINE) of Kyushu Institute of Technology, Japan in collaboration with Nanyang Technological University, Singapore to measure the electron density distribution using a constellation of intercommunicating Cube-Satellites equipped with a highly precise atomic clock in different LEO orbits and a network of ground stations. SPATIUM-I is currently in orbit down-linking signals to be processed in the ground station, SPATIUM-II is currently under development to demonstrate the on-board processing of Up-link signals to the satellite.

Scopus

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

©2019. American Geophysical Union. All Rights Reserved. We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures “remotely,” whereas RBSP-B observed them “locally.”.

DOI： 10.1029/2019GL084379

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2019. American Geophysical Union. All Rights Reserved. We present the first and direct comparison between magnetospheric plasma waves and polar mesosphere winter echoes (PMWE) simultaneously observed by the conjugate observation with Arase satellite and high-power atmospheric radars in both hemispheres, namely, the Program of the Antarctic Syowa Mesosphere, Stratosphere, and Troposphere/Incoherent Scatter Radar at Syowa Station (SYO; −69.00°S, 39.58°E), Antarctica, and the Middle Atmosphere Alomar Radar System at Andøya (AND; 69.30°N, 16.04°E), Norway. The PMWE were observed during 03–07 UT on 21 March 2017, just after the arrival of corotating interaction region in front of high-speed solar wind stream. An isolated substorm occurred at 04 UT during this interval. Electromagnetic ion cyclotron (EMIC) waves and whistler mode chorus waves were simultaneously observed near the magnetic equator and showed similar temporal variations to that of the PMWE. These results indicate that chorus waves as well as EMIC waves are drivers of precipitation of energetic electrons, including relativistic electrons, which make PMWE detectable at 55- to 80-km altitude. Cosmic noise absorption measured with a 38.2-MHz imaging riometer and low-altitude echoes at 55–70 km measured with an medium-frequency radar at SYO also support the relativistic electron precipitation. We suggest a possible scenario in which the various phenomena observed in near-Earth space, such as magnetospheric plasma waves (EMIC waves and chorus waves), pulsating auroras, cosmic noise absorption, and PMWE, can be explained by the interaction between the high-speed solar wind containing corotating interaction regions and the magnetosphere.

DOI： 10.1029/2019JA026891

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2019. American Geophysical Union. All Rights Reserved. Molecular ions in the magnetosphere can be a tracer of fast ion outflows from the deep ionosphere. Statistical properties of molecular ions (O2+/NO+/N2+) in the ring current are investigated based on ion composition measurements (<180 keV/q) by medium-energy particle experiments-electron analyzer and low-energy particle experiments-ion mass analyzer instruments on board the Arase (Exploration of energization and Radiation in Geospace, ERG) satellite. The investigated period from late March to December 2017 includes 11 geomagnetic storms with the minimum Dst index less than −40 nT. The molecular ions are observed in the region of L = 2.5–6.6 and clearly identified at energies above ~12 keV during most magnetic storms. During quiet times, molecular ions are not observed. The average energy density ratio of the molecular ions to O+ is ~3%. The ratio tends to increase with the size of magnetic storms. Existence of molecular ions even during small magnetic storms suggests that the fast ion outflow from the deep ionosphere occurs frequently during geomagnetically active periods.

DOI： 10.1029/2019GL084163

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2019. American Geophysical Union. All Rights Reserved. We examined the average meridional distribution of middle-energy protons (10–180 keV) and pressure-driven currents in the nightside (20–04 hr magnetic local time) ring current region during moderately disturbed times using the Arase satellite's data. Because the Arase satellite has a large inclination orbit of 31°, it covers the magnetic latitude (MLAT) in the range of −40° to 40° and a radial distance of <6RE. We found that the plasma pressure decreased significantly with increasing MLAT. The plasma pressure on the same L* shell at 30° < MLAT < 40° was ∼10–60% of that at 0° < 4 MLAT < 10°, and the rate of decrease was larger on lower L* shells. The pressure anisotropy, derived as the perpendicular pressure divided by the parallel pressure minus 1, decreased with radial distance and showed a weak dependence on MLAT. The magnitude of the plasma beta at 30°<MLAT<40° was 1 or 2 orders smaller than that at 0°<MLAT<10°. The plasma pressure normalized by the value at 0°<MLAT<10° estimated from the magnetic strength and anisotropy was roughly consistent with the observed plasma pressure for L*=3.5–5.5. The azimuthal pressure-gradient current derived from the plasma pressure was distributed over MLAT∼0–20°, while the curvature current was limited within MLAT∼0–10°. We suggest that the latitudinal dependence should be taken into account in interpretations of plasma parameters in successive orbits during magnetic storms.

DOI： 10.1029/2019JA026682

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記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）

We investigated the difference between the magnetic field observed by the Arase spacecraft and the Tsyganenko 89 model field (ΔB) during geomagnetic quiet period to determine the DC component of spacecraft-origin magnetic field noise at the position of Magnetic Field Experiment (MGF) onboard the Arase spacecraft. The median value of the Z-component of ΔB in the Despun Sun sector Inertia (DSI) coordinates is very small (-0.6 nT); therefore, MGF has a good magnetic field cleanness and is well-calibrated. We also found that the Z-component of the magnetic field in the SM coordinate system observed by Arase is usually larger than that of the model field by - 3 nT. The difference between time periods for the data used in this study and for the data to create the Tsyganenko 89 model may cause the discrepancy.

DOI： 10.20637/JAXA-RR-18-005E/0004

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記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）

The evaluation of the spacecraft-origin magnetic field noise (B_sub(DCnoise)) at the position of the sensor of Magnetic Field Experiments (MGF) onboard the Arase satellite has been performed. We examined the difference between the observation of the magnetic field with MGF and the Tsyganenko-Sitnov 04 (TS04) model field in DSI coordinates (ΔB sub(DSI)) during the quiet time intervals. ΔB sub(z, DSI) was - 0.7 nT on average, which indicates that the B_sub(DCnoise) in the spin-axis direction is quite small. We conclude that the MGF data are well-calibrated and no large B_sub(DCnoise) is included in the measured magnetic field. Although the difference between the MGF observations and the TS04 model in the X sub(DSI) and Y sub(DSI) directions was a few nT, it may be attributed to the TS04 model field, not an observational error of MGF.

DOI： 10.20637/JAXA-RR-18-005E/0005

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）

Herein, ground calibration experiments were performed to determine the sensitivity for all components and the angles (alignment) between the measurement axes of the magnetic field experiment (MGF) onboard Arase satellite. We can well determine the sensitivities within 0.07 % error and the alignment within 90 +/- 1 deg with - 0.03deg accuracy. Also, the temperature dependences of the offset and sensitivity were examined. Results revealed that the relative sensitivity to the room temperature can be fit with a linear regression line. The offsets exhibited systematical dependences on temperatures. Between March 13, 2017 and April 30, 2018, when MGF with an 8000-nT range mostly measured ambient magnetic field in orbit at -10 C-0 C, the linearity of sensitivity and offset with a standard error of less than 0.00023 and less than 0.67 nT, respectively, was determined. The measured sensitivity, alignment, and offset were used to measure the magnetic field with high accuracy, thereby meeting the MGF capability and performance requirement of the field intensity less than 5 nT and the field direction error less than 1 deg.

DOI： 10.20637/JAXA-RR-18-005E/00031

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記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）

Precise magnetic field measurement is aimed in the Arase project to investigate the growth and decline of the earth radiation belt. The sensing directions of the magnetometer sensor elements in the spacecraft reference frame are calculated by the analysis of the in-orbit magnetic field data. They are determined with good accuracies, within 0.05 deg and 0.2 deg for the +/-8000 nT and +/-60000 nT measurement ranges, respectively. The misalignment angles are continuously varying with the time, and the variation is supposed to be caused by the mechanical deformation of the extendable MAST on which the magnetometer sensor is mounted.

DOI： 10.20637/JAXA-RR-18-005E/0003

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記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）

The high-resolution magnetic field measurement in the intense field is required for the achievement of the Arase project. The magnetometer (MGF) onboard Arase has the digital resolution of 20 bit, which is realized by the 20-bit analogue-to-digital conversion (ADC). A delta-sigma ADC circuit has been developed to satisfy the 20-bit resolution, 256 Hz sampling and tolerance for the severe radiation environment in the radiation belt. We performed the ground experiment at a room temperature to evaluate the non-linearity characteristics of the delta-sigma ADC used for MGF. The non-linearity error for the full range was measured by obtaining continuously the output digital values from ADC for gradually varying input analogue voltage. The maximum non-linear error was 781 digits (0.07% of the full range) corresponding to 11 nT (84 nT) for +/-8000 nT (+/-60000 nT) measurement range. The deviation was determined within 103 digits, corresponding to 1.5 nT (11.0 nT) for +/-8000 nT (+/-60000 nT) range, when the environmental interference noise was not intense. It is within 213 digits, corresponding to 3.1 nT (22.5 nT) for +/-8000 nT (+/-60000 nT) range, when the environmental noise was significant.

DOI： 10.20637/JAXA-RR-18-005E/0002

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2019, The Author(s). Substorm-associated electron injection, starting on Apr. 5, 2017, was observed by the ERG (Arase), GOES-15 and GOES-13 spacecraft. ERG successfully observed a clear and sufficient extent of manifestations of the dispersionless injection and the successive drift echoes at radial distances shorter than geosynchronous orbit (GEO) during a unique period of the satellite mission. The GOES-15 and GOES-13 measured the drift echoes of the event as well. The observations provided constraints to study the event and opportunities to make adjustments to the previous substorm injection models. Models built on an impulsive earthward-propagating electromagnetic field have been proposed to simulate substorm injections. So far such models showed good results of dispersionless features compared to spacecraft observations, but could only produce drift echoes with periods somewhat different from geosynchronous observations. To study the substorm injection event and produce drift echoes with better periods, we modify an existing model in the literature. ERG and GOES spacecraft measured tens to a few hundred keV electrons injected during the substorm, providing important seed population for ring current and radiation belts. Since the electron energies of interest are comparable to the rest mass energy, our work further provides the relativistic form of the previous model and employs a semiempirical model as background field instead of a dipole-based one in the previous study. Our work shows that the main features of the substorm injection event are successfully reproduced with the drift echoes periods showing a better fit to the observations of this event when relativistic effects are considered. Despite possible deviation of the model magnetic fields from reality, the relativistic computations still show dominant effect on the drift echoes periods. The substorm injection expanding earthward farther than GEO was observed by ERG, and the event can be better simulated by the further-developed model shown in this work.

DOI： 10.1186/s40623-019-0999-5

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）

宇宙機に搭載したベクトル磁力計を用いて、宇宙空間における磁場を精度良く観測するためには、絶対座標における磁場測定方向を高精度で決定する必要がある。このためには、絶対座標における宇宙機の姿勢を高精度で求めると同時に、宇宙機の機軸座標における磁場測定方向（アライメント）を高精度で求める必要がある。宇宙機がスピンしている場合には、ベクトル磁力計の3 成分のデータは正弦波の時間変動を示し、その振幅と位相を使って、スピン軸を基準とした機軸座標における磁力計のアライメントを算出することが可能である。磁力計の地上較正で、各測定軸の感度と測定軸間のなす角が既に求められている場合、アライメントを表す2 つの角度と、スピン面内の磁場の2 成分の合計4 つの未知数に対し、これらの間の関係を表す式は6 つ立ち、3 通りのアライメントの解が求められる。ここで示した手法を、ジオスペース探査衛星「あらせ」搭載の磁場観測器MGF によって実際に得られたデータに適用した。±8000 nT レンジの時には0.05度、±60000 nT レンジの時には0.2度の精度でアライメントを求められることが示された。

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2019, The Author(s). With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (www.spedas.org), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have “crib-sheets,” user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer’s Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its “modes of use” with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans.

DOI： 10.1007/s11214-018-0576-4

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. In the inner magnetosphere, the Arase spacecraft has observed electromagnetic ion cyclotron (EMIC) emissions with both rising and falling frequencies. The instantaneous frequency analyses on the electromagnetic fields of the EMIC rising tone emission have been performed by the Hilbert-Huang transform. The time variation of the instantaneous frequency shows a good agreement with the nonlinear theory for the frequency evolutions. Rapid instantaneous frequency modulation is also found during the rising tone emission. We estimate the peak-to-peak time of the fluctuation in the frequency and find that the fluctuation is caused around a half of the particle trapping time. From the motion of the phase-bunched particle around the resonant velocity, it is expected that the nonlinear resonant current, which induces the falling frequency is formed in half the trapping time.

DOI： 10.1029/2018GL079765

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018, The Author(s). The Exploration of energization and Radiation in Geospace (ERG) Science Center serves as a hub of the ERG project, providing data files in a common format and developing the space physics environment data analysis software and plug-ins for data analysis. The Science Center also develops observation plans for the ERG (Arase) satellite according to the science strategy of the project. Conjugate observations with other satellites and ground-based observations are also planned. These tasks contribute to the ERG project by achieving quick analysis and well-organized conjugate ERG satellite and ground-based observations.[Figure not available: see fulltext.]

DOI： 10.1186/s40623-018-0867-8

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. We surveyed 378 electromagnetic ion cyclotron (EMIC) wave events using Arase during the first 12 months. We discriminated the observed EMIC waves into two types (fine-structured EMIC waves and unstructured EMIC waves), according to whether or not they exhibited clear periodic amplitude modulations. We found a clear afternoon peak in the occurrence probability of unstructured EMIC waves in the region of L = 5–9. Fine-structured EMIC waves were mainly distributed in the off-equatorial region, and their occurrence probability was clearly high around the noon sector. Such noon sector EMIC wave peaks had not been found in the THEMIS, AMPTE, or Cluster measurements, due to their limited L shell coverages. The Van Allen probes, too, were not able to measure the major region of fine-structured EMIC waves because of their limited latitudinal coverage. Our unique statistical results demonstrate the importance of discriminating the wave structures as well as of performing observations over a wide range of latitudes.

DOI： 10.1029/2018GL080109

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. Storm-time region-2 field-aligned currents (R2 FACs) are believed to be connected between the ring current region and the ionosphere, but this connection has not been clarified by simultaneous in situ observations. We confirmed the connection of upward R2 FACs during 16 July and 18 June 2017 storm events using coordinated magnetic observations by the Arase satellite in medium-Earth orbit and the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). The upward FACs were determined by drastic changes in the azimuthal magnetic field at Arase in the off-equatorial (3- to 4-R E radial distance and 1–2 R E above the magnetic equator) postmidnight inner magnetosphere. The magnetic latitude of the FAC observed by Arase projected onto the ionosphere was consistent with that of the ionospheric FAC observed by the AMPERE. Using the conservation of the ratio between the current density and the total magnetic field along the field line, we showed that the current between Arase and AMPERE was almost conserved, meaning that a large portion of the R2 FAC was generated in the low-latitude inner magnetosphere. We also calculated the plasma pressures of H + and O + ions and pressure-driven currents to examine their relationship for the first event. The O + pressure contributed significantly to the inner part of the total azimuthal current. The peaks of combined pressure of H + and O + , and pressure-driven currents were located inside and outside the FAC, respectively. A simple model calculation indicated that this spatial relationship is controlled by the day-night asymmetry of magnetic field.

DOI： 10.1029/2018JA025865

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. This paper reports two unique auroral features: postmidnight purple auroral rays and global Pc1 geomagnetic pulsations, observed before the onset of the corotating interaction region (CIR) storm of 21 March 2017, at the beginning of the first campaign of the new Particles and Waves in the Inner magnetosphere using Ground-based network observation (PWING) longitudinal ground network with the Arase satellite. The purple auroral rays were observed from ~0315 to 0430 UT (~03–04 magnetic local time) in the northeastern sky at Husafell, Iceland (magnetic latitude: 64.9°N). We newly propose that the entry of high-density CIR plasma into the magnetotail created purple auroral rays in the sunlit ionosphere. Pc1 geomagnetic pulsations at frequencies of 0–0.5 Hz were observed after ~00 UT over a wide local time range, of 13 hr, from midnight to afternoon sectors at subauroral latitudes associated with CIR arrival. These results indicate preconditioning of the magnetosphere due to crossing of a CIR.

DOI： 10.1029/2018GL079103

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. In this study, we describe small-scale density depletions of cold electrons associated with electrostatic electron cyclotron harmonic (ECH) waves observed by the ERG (Exploration of energization and Radiation in Geospace) spacecraft during a plasmapause crossing near the magnetic equator in the postmidnight sector. The total electron density was roughly 2 orders of magnitude larger than that of the hot electrons, indicating existence of a cold and dense electron population below ∼20 eV. The cold electron density profile showed small-scale density depletion regions, in which the ECH emissions were intensified. Moreover, a flux enhancement of hot electrons in the perpendicular direction was also associated with the ECH emissions intensity. This relation suggests perpendicular energization of electrons by electric field oscillation of the ECH waves.

DOI： 10.1029/2018GL080117

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00–07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9–5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15% O + ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10–07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O + density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent-shaped torus or a pinched torus.

DOI： 10.1029/2018GL080122

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. During 26–29 March 2017 magnetic storm, the Arase satellite observed typical ultra low frequency (ULF) waves and acceleration of relativistic electrons. We simulate the global distribution of these ULF waves using CRCM with BATSRUS global magnetospheric magnetohydrodynamic model. The simulation can qualitatively reproduce the ULF waves observed by Arase at frequencies of 2–3 mHz. However, the simulated ULF wave power is 1–2 orders of magnitude smaller than the observation. The simulated ULF wave activity has a good correlation with the solar-wind dynamic pressure variation, while the wave activity on the ground is enhanced even during the recovery phase, possibly due to the Kelvin-Helmholtz instability and/or substorms. We also study the 3–6 April 2017 magnetic storm, in which low ULF wave activity and weak acceleration of relativistic electrons are seen. We suggest that the existence of ULF waves plays an important role in accelerating electrons up to relativistic energies.

DOI： 10.1029/2018GL078857

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. Super Dual Auroral Radar Network (SuperDARN) observations show that ionospheric flow fluctuations of millihertz or lower-frequency range with horizontal velocities of a few hundred meters per second appeared in the subauroral to midlatitude region during a magnetic storm on 27 March 2017. A set of the radars have provided the first ever observations that the fluctuations propagate azimuthally both westward and eastward simultaneously, showing bifurcated phase propagation associated with substorm expansion. Concurrent observations near the conjugate site in the inner magnetosphere made by the Arase satellite provide evidence that multiple drifting clouds of electrons in the near-Earth equatorial plane were associated with the electric field fluctuations propagating eastward in the ionosphere. We interpret this event in terms of mesoscale pressure gradients carried by drifting ring current electrons that distort field lines one after another as they drift through the inner magnetosphere, causing eastward propagating ionospheric electric field fluctuations.

DOI： 10.1029/2018GL079777

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2018 International Union of Radio Science URSI. The Electromagnetic ion cyclotron (EMIC) wave is one of the key phenomena to understand the loss dynamics of MeV-energy electrons in the Earth's radiation belt. The precipitation into the ionosphere of MeV-energy electrons was observed in the isolated proton aurora which is an ionospheric footprint for the region of EMIC wave-particle interaction in the magnetosphere [1]. However, it is still unclear how significant the EMIC wave is in terms of the global scale of the whole radiation belt, and it is important to understand where and when the preferable condition is set in the radiation belt of the inner magnetosphere for strong EMIC waves.

DOI： 10.23919/URSI-AT-RASC.2018.8471561

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2018 International Union of Radio Science URSI. The electromagnetic ion cyclotron (EMIC) waves are generated by the temperature anisotropy of protons. Especially, the nonlinear wave particle interaction [1], [2] between the EMIC waves and protons causes the rising or falling frequencies and drastic proton scattering in the equatorial region[3]. Frequency sweep rate of the EMIC wave is a key parameter to analyze the affection on the ion scattering, however the estimation of the sweep rate is difficult from the Fourier dynamic spectrum due to the limitation between the frequency and temporal resolutions.

DOI： 10.23919/URSI-AT-RASC.2018.8471543

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. The Arase spacecraft is capable of observing ultralow frequency waves in the inner magnetosphere at intermediate magnetic latitudes, a region sparsely covered by previous spacecraft missions. We report a series of impulsively excited fundamental toroidal mode standing Alfvén waves in the midnight sector observed by Arase outside the plasmasphere at magnetic latitudes 13–24°. The wave onsets are concurrent with Pi2 onsets detected by the Van Allen Probe B spacecraft at the magnetic equator in the duskside plasmasphere and by ground magnetometers at low latitudes. The duration of each toroidal wave packet is ∼20 min, which is much longer than that of the corresponding Pi2 wave packet. The toroidal waves cannot be the source of high-latitude Pi2 waves because they were not detected on the ground near the magnetic field footprint of Arase. Overall, the toroidal wave event lasted more than 2 hr and allowed us to use the wave frequency to estimate the plasma mass density at L = 6.1–8.3. The mass density (in amu/cm3) is higher than the electron density (cm−3) by a factor of ∼6, which implies that 17–33% of the ions were O+.

DOI： 10.1029/2018GL078731

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. The Arase satellite observed clear dipolarization signatures at r~4.3–4.6 RE, GMLAT~16°–18°, and MLT~5.5–5.7 hr around 15:00 UT on 27 March 2017 when Dst~−70 nT. Strong magnetic field fluctuations were embedded and their characteristic frequency was close to the local gyrofrequency of O+ ions. After the dipolarization, O+ flux was enhanced at ≤15 keV, while H+ flux showed no clear variations. These observations provide evidence for the direct supply of O+ ions from the ionosphere. There were no clear signatures for the nonadiabatic local acceleration of O+ ions. We consider that a bump-on-tail structure in the energy spectrum around 30–50 keV due to a combination of charge exchange loss and drift motion of ions masks the nonadiabatic acceleration. Occurrence of the magnetic field dipolarization at dawn, which is far from the well-known premidnight occurrence peak, may be due to an eastward skewing of partial ring current during the storm main phase.

DOI： 10.1029/2018GL078825

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. A Pc5 wave is observed by the Exploration of energization and Radiation in Geospace Arase satellite in the inner magnetosphere (L ~5.4–6.1) near postmidnight (L-magnetic local time ~1.8–2.5 hr) during the storm recovery phase on 27 March 2017. Its azimuthal wave number (m-number) is estimated using two independent methods with satellites and ground observations to be −8 to −15. The direct measurement of the m-number enables us to calculate the resonance energy. The flux oscillations of H+ and O+ ions at ≥ 56.3 keV are caused by drift resonance and those of O+ ions at ≤ 18.6 keV by bounce resonance. Resonances of O+ ions at multiple energies are simultaneously observed for the first time. The enhancement of the O+/H+ flux ratio at ≤ 18.6 keV indicates selective acceleration of O+ ions through bounce resonance.

DOI： 10.1029/2018GL078961

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記述言語：英語   掲載種別：研究論文（学術雑誌）

©2018. American Geophysical Union. All Rights Reserved. We present observational evidence of drift resonance between westward propagating odd mode standing ultralow frequency waves and energetic protons. Compressional ∼13 mHz (Pc4 band) waves and proton flux oscillations at >50 keV were detected at ∼03 hr magnetic local time by the Arase satellite on 15 April 2017. The azimuthal wave number (m number) is estimated to be ∼−50 from ground observations, while the theory of drift resonance gives m ∼− 49 for odd mode waves and ∼110-keV protons, providing evidence that the drift resonance indeed took place in this event. We also found a steep earthward gradient of proton phase space density, which can quantitatively explain the wave excitation. The observed waves show typical features of giant pulsations (Pgs), regarding local time, m number, and flux oscillations. This study, therefore, has great implications to the field line mode structure and excitation mechanism of Pgs.

DOI： 10.1029/2018GL078293

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018, The Author(s). The fluxgate magnetometer for the Arase (ERG) spacecraft mission was built to investigate particle acceleration processes in the inner magnetosphere. Precise measurements of the field intensity and direction are essential in studying the motion of particles, the properties of waves interacting with the particles, and magnetic field variations induced by electric currents. By observing temporal field variations, we will more deeply understand magnetohydrodynamic and electromagnetic ion-cyclotron waves in the ultra-low-frequency range, which can cause production and loss of relativistic electrons and ring-current particles. The hardware and software designs of the Magnetic Field Experiment (MGF) were optimized to meet the requirements for studying these phenomena. The MGF makes measurements at a sampling rate of 256 vectors/s, and the data are averaged onboard to fit the telemetry budget. The magnetometer switches the dynamic range between ± 8000 and ± 60,000 nT, depending on the local magnetic field intensity. The experiment is calibrated by preflight tests and through analysis of in-orbit data. MGF data are edited into files with a common data file format, archived on a data server, and made available to the science community. Magnetic field observation by the MGF will significantly improve our knowledge of the growth and decay of radiation belts and ring currents, as well as the dynamics of geospace storms.[Figure not available: see fulltext.].

DOI： 10.1186/s40623-018-0800-1

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017, The Author(s). This paper summarizes the specifications and initial evaluation results of Wire Probe Antenna (WPT) and Electric Field Detector (EFD), the key components for the electric field measurement of the Plasma Wave Experiment (PWE) aboard the Arase (ERG) satellite. WPT consists of two pairs of dipole antennas with ~ 31-m tip-to-tip length. Each antenna element has a spherical probe (60 mm diameter) at each end of the wire (15 m length). They are extended orthogonally in the spin plane of the spacecraft, which is roughly perpendicular to the Sun and enables to measure the electric field in the frequency range of DC to 10 MHz. This system is almost identical to the WPT of Plasma Wave Investigation aboard the BepiColombo Mercury Magnetospheric Orbiter, except for the material of the spherical probe (ERG: Al alloy, MMO: Ti alloy). EFD is a part of the EWO (EFD/WFC/OFA) receiver and measures the 2-ch electric field at a sampling rate of 512 Hz (dynamic range: ± 200 mV/m) and the 4-ch spacecraft potential at a sampling rate of 128 Hz (dynamic range: ± 100 V and ± 3 V/m), with the bias control capability of WPT. The electric field waveform provides (1) fundamental information about the plasma dynamics and accelerations and (2) the characteristics of MHD and ion waves in various magnetospheric statuses with the magnetic field measured by MGF and PWE–MSC. The spacecraft potential provides information on thermal electron plasma variations and structure combined with the electron density obtained from the upper hybrid resonance frequency provided by PWE–HFA. EFD has two data modes. The continuous (medium-mode) data are provided as (1) 2-ch waveforms at 64 Hz (in apoapsis mode, L > 4) or 256 Hz (in periapsis mode, L < 4), (2) 1-ch spectrum within 1–232 Hz with 1-s resolution, and (3) 4-ch spacecraft potential at 8 Hz. The burst (high-mode) data are intermittently obtained as (4) 2-ch waveforms at 512 Hz and (5) 4-ch spacecraft potential at 128 Hz and downloaded with the WFC-E/B datasets after the selection. This paper also shows the initial evaluation results in the initial observation phase.[Figure not available: see fulltext.].

DOI： 10.1186/s40623-017-0760-x

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）

ジオスペース探査（ERG）衛星に搭載される磁場観測器(MGF)のセンサ部(MGF-S)の地上較正試験を行い、感度とアライメントを決定した。MGF-Sに磁場を印加し出力値を測定することにより、誤差0.06%以内の高い精度でMGF-Sの感度を決定することができた。また、MGF-Sの軸間角度は直交から0.95度以内のずれを持ちその推定誤差は0.07度以内であった。MGF-Sのオフセットと感度の温度依存性を調べたところ、室温に対する相対感度は-20度Cから30度Cの間で、温度の差に対してほぼ直線的に変化することがわかった。一方、オフセットは温度に対し直線的な変化は見られなかったものの、再現性があることがわかった。以上の地上較正試験によって得られた感度とアライメント及びオフセットの決定精度はERGの観測期間の大部分で観測要求を十分に満たすことがわかった。

記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2016 Teramoto et al. We herein describe a harmonic Pi2 wave that started at 09:12 UT on August 19, 2010, with data that were obtained simultaneously at 19:00-20:00 MLT by three mid-latitude Asian-Oceanian Super Dual Auroral Radar Network (SuperDARN) radars (Unwin, Tiger, and Hokkaido radars), three Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites (THEMIS A, THEMIS D, and THEMIS E), and ground-based magnetometers at low and high latitudes. All THEMIS satellites, which were located in the plasmasphere, observed Pi2 pulsations dominantly in the magnetic compressional (B //) and electric azimuthal (E A) components, i.e., the fast-mode component. The spectrum of Pi2 pulsations in the B // and E A components contained two spectral peaks at approximately 12 to 14 mHz (f 1, fundamental) and 23 to 25 mHz (f 2, second harmonic). The Poynting flux derived from the electric and magnetic fields indicated that these pulsations were waves propagating earthward and duskward. Doppler variations (V) from the 6-s or 8-s resolution camping beams of the Tiger and Unwin SuperDARN radars, which are associated with Pi2 pulsations in the eastward electric field component in the ionosphere, observed Pi2 pulsations within and near the footprint of the plasmapause, whose location was estimated by the THEMIS satellites. The latitudinal profile of f 2 power normalized by f 1 power for Doppler velocities indicated that the enhancement of the normalized f 2 power was the largest near the plasmapause at an altitude-adjusted corrected geomagnetic (AACGM) latitude of 60° to 65°. Based on these features, we suggest that compressional waves propagate duskward away from the midnight sector, where the harmonic cavity mode is generated.

DOI： 10.1186/s40623-016-0397-1

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We investigated Pi2 pulsations in the nightside ionosphere that began at 14:15 UT (2315 LT) on 11 July 2010, and they were observed with high-temporal (8 s) resolution by beam 4 of the Super Dual Auroral Radar Network (SuperDARN) Hokkaido radar. These pulsations were simultaneously observed in both the ground/sea scatter echoes reflected from the F region height and in ionospheric echoes from field-aligned irregularities in the sporadic Es region. They had the same period of 110 s and approximately no phase lag. From the radar observations and the International Geomagnetic Reference Field model, the amplitude of the eastward (EEW) component of the electric field of the Pi2 pulsations in the ionosphere was estimated ~8.0 mV/m in the F region and ~2.0 mV/m in the E region. Corresponding Pi2 pulsations appeared dominantly in the horizontal northward magnetic field component (H) at nearby ground stations, Moshiri (MSR), St. Paratunka (PTK), and Stecolny (STC), with amplitudes ranging from 6 nT (MSR) to 10 nT (STC). At the dominant frequency of 8.8 mHz, the coherences between H and EEW were high (>0.9), the cross phases of EEW relative to H were -56° and -45°, and the amplitude ratios were 2.7 × 105 m/s and 8.4 × 105 m/s, in the E and F regions, respectively. Based on a comparison of these results with theoretical predictions, we suggest that the concept of a pure cavity mode is not sufficient to explain the combined observations for midlatitude Pi2 waves and that the contribution of an Alfvén waves must be taken in account. Key Points Midlatitude SuperDARN radar observed Pi2 pulsations in the E and F regions The electric field of Pi2 pulsations in the ionosphere are estimated The conception of pure cavity mode is not sufficient ©2014. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2012JA018585

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The interpretation of simultaneous ionospheric Doppler sounding and ground magnetometer observations of low-latitude Pi2 waves is revised. We compare the theoretical estimates of the ionospheric Doppler velocity for the same amplitude of the ground magnetic disturbances produced by a large-scale compressional mode and an Alfvén mode. The plasma vertical displacement caused by the wave electric field is shown to be the dominating effect. Taking into account the correction of the previous paper, the observations of low-latitude Pi2 in the F layer ionosphere by Doppler sounding and SuperDARN (Super Dual Auroral Radar Network) radars give consistent results. We suggest that the Doppler response to Pi2 waves is produced by the Alfvén wave component, but not the fast-mode component, whereas the ground magnetic signal is composed from both Alfvén and fast magnetosonic modes. © Author(s) 2013.

DOI： 10.5194/angeo-31-689-2013

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We statistically studied the spatial characteristics of Pi2 pulsations using magnetic field observations in the magnetosphere at the equatorial-orbiting Active Magnetospheric Particle Tracer Explorers (AMPTE)/Charge Composition Explorer (CCE) and the polar-orbiting Dynamics Explorer 1 (DE 1) satellites and on the ground at the low-latitude station Kakioka (KAK, L = 1.23). We defined Pi2 pulsations from wavelet analysis of KAK data covering August 1984 to January 1989 and obtained 849 nightside (20:00-04:00 LT) events. For each KAK Pi2 event, we evaluated the coherence between the ground H component and the magnetospheric radial (B ⊥R), azimuthal (B⊥A), and compressional (B ∥) components at the frequency of the ground Pi2. High-coherence ground-satellite Pi2 events were found most often in B∥, with many of them evident at both spacecraft when CCE was located near the equator (magnetic latitude <30°) and inside of the plasmapause estimated from an empirical formula while DE 1 was located at high latitude (>30°) and outside of the estimated plasmapause. In these simultaneous CCE and DE 1 events, the B∥ amplitude was larger at CCE; in addition, the H-B ∥ cross phase was ∼0° at CCE but was ∼180° at DE 1. We show detailed analysis of one such event as well as two other events that occurred when CCE was outside of the estimated plasmapause and exhibited different coherence and cross-phase properties at this spacecraft. Overall, the two-satellite observations provide additional evidence of plasmaspheric virtual resonance, which was previously suggested from studies using single satellites. Copyright © 2011 by the American Geophysical Union.

DOI： 10.1029/2010JA016199

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have statistically analyzed Pi2 pulsations, using the 6-second magnetic field data acquired by the polar orbiting DE-1 satellite (a perigee of about 500 km altitude and an apogee of about 3.6 RE altitude). From February 1983 to January 1991, 746 events were found in the H component of the geomagnetic field data from Kakioka or Hermanus, which were located near midnight at substorm onsets determined with the AL index. Out. of these 746 events, 91 events had high coherence (>0.6) between DE-1 and ground stations. We examined the spatial distributions of the occurrence probability and the L dependence of the power ratio to the ground and phase difference. The following observational results are obtained: (1) There are many high-coherence events in the compressional component at high latitude as well as at low latitude on the nightside; (2) In the congressional component, the power ratio of DE-1 to ground stations has a weak peak around L ∼5 on the nigthside and flankside; and (3) the phase difference between DE-1 and ground stations is changed by ∼180° around L ∼5 on the nightside and flankside. Some high-coherence events were found in the compressional component in the polar region. We concluded Pi2 pulsations might be excited by plasmaspheric virtual resonance (PVR) mode, in which compressional waves are produced inside the plasmasphere and oscillate the ambient magnetic field at high latitude. Copyright 2008 by the American Geophysical Union.

DOI： 10.1029/2007JA012740

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開催期間： 2018年11月23日 - 2018年11月27日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2018年11月23日 - 2018年11月27日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2018年11月23日 - 2018年11月27日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2018年11月23日 - 2018年11月27日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2018年06月21日 - 2018年06月22日   記述言語：英語   開催地：Santa Fe, USA.  

開催期間： 2018年06月21日 - 2018年06月22日   記述言語：英語   開催地：Santa Fe, USA.  

開催期間： 2018年06月03日 - 2018年06月08日   記述言語：英語   開催地：Honolulu, Hawai, USA  

開催期間： 2018年06月03日 - 2018年06月08日   記述言語：英語   開催地：Honolulu, Hawai, USA  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   記述言語：日本語   開催地：幕張、千葉  

開催期間： 2018年01月11日   記述言語：日本語   開催地：相模原、神奈川、日本  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年12月11日 - 2017年12月15日   記述言語：英語   開催地：New Orleans, LA, USA  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：英語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年10月15日 - 2017年10月19日   記述言語：日本語   開催地：宇治, 京都, 日本  

開催期間： 2017年09月05日 - 2017年09月08日   記述言語：英語   開催地：Taipei & Tainana, Taiwan  

開催期間： 2017年09月05日 - 2017年09月08日   記述言語：英語   開催地：Taipei & Tainana, Taiwan  

開催期間： 2017年05月20日 - 2017年05月25日   記述言語：英語   開催地：Makuhari, Chiba, Japan  

開催期間： 2017年05月20日 - 2017年05月25日   記述言語：日本語   開催地：Makuhari, Chiba, Japan  

開催期間： 2017年05月20日 - 2017年05月25日   記述言語：日本語   開催地：Makuhari, Chiba, Japan  

開催期間： 2016年11月19日 - 2016年11月23日   記述言語：日本語   開催地：福岡、日本  

開催期間： 2016年11月19日 - 2016年11月23日   記述言語：日本語   開催地：福岡、日本  

開催期間： 2016年11月19日 - 2016年11月23日   記述言語：日本語   開催地：福岡、日本  

開催期間： 2016年05月22日 - 2016年05月26日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2016年05月22日 - 2016年05月26日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2016年05月22日 - 2016年05月26日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2015年10月31日 - 2015年11月03日   記述言語：日本語   開催地：東京、日本  

開催期間： 2015年10月31日 - 2015年11月03日   記述言語：日本語   開催地：東京、日本  

開催期間： 2015年10月31日 - 2015年11月03日   記述言語：日本語   開催地：東京、日本  

開催期間： 2015年08月10日 - 2015年08月11日   記述言語：日本語   開催地：京都、日本  

開催期間： 2015年08月02日 - 2015年08月07日   記述言語：英語   開催地：Singapore  

開催期間： 2015年05月24日 - 2015年05月28日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2015年05月24日 - 2015年05月28日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2015年05月24日 - 2015年05月28日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2015年03月13日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2015年03月13日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2015年01月06日 - 2015年01月07日   記述言語：日本語   開催地：相模原、神奈川、日本  

開催期間： 2015年01月06日 - 2015年01月07日   記述言語：日本語   開催地：相模原、神奈川、日本  

開催期間： 2015年01月06日 - 2015年01月07日   記述言語：日本語   開催地：相模原、神奈川、日本  

開催期間： 2014年11月10日 - 2014年11月14日   記述言語：英語   開催地：Ise, Mie, Japan  

開催期間： 2014年10月31日 - 2014年11月03日   記述言語：日本語   開催地：松本、長野、日本  

開催期間： 2014年10月31日 - 2014年11月03日   記述言語：日本語   開催地：松本、長野、日本  

開催期間： 2014年08月18日 - 2014年08月19日   記述言語：日本語   開催地：立川、東京、日本  

開催期間： 2014年04月28日 - 2014年05月02日   記述言語：日本語   開催地：横浜、神奈川、日本  

開催期間： 2014年04月28日 - 2014年05月02日   記述言語：日本語   開催地：横浜、神奈川、日本  

開催期間： 2014年04月28日 - 2014年05月02日   記述言語：日本語   開催地：横浜、神奈川、日本  

開催期間： 2014年01月09日 - 2014年01月10日   記述言語：日本語   開催地：相模原、神奈川、日本  

開催期間： 2013年11月18日 - 2013年11月22日   記述言語：英語   開催地：Nagoya, Aichi, Japan  

開催期間： 2013年11月18日 - 2013年11月22日   記述言語：英語   開催地：Nagoya, Aichi, Japan  

開催期間： 2013年11月18日 - 2013年11月22日   記述言語：英語   開催地：Nagoya, Aichi, Japan  

開催期間： 2013年11月02日 - 2013年11月05日   記述言語：日本語   開催地：高知、日本  

開催期間： 2013年11月02日 - 2013年11月05日   記述言語：日本語   開催地：高知、日本  

開催期間： 2013年11月02日 - 2013年11月05日   記述言語：日本語   開催地：高知、日本  

開催期間： 2013年05月19日 - 2013年05月24日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2013年05月19日 - 2013年05月24日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2013年05月19日 - 2013年05月24日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2013年05月19日 - 2013年05月24日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2013年05月19日 - 2013年05月24日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2013年01月28日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2013年01月28日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2013年01月28日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2013年01月28日   記述言語：日本語   開催地：名古屋、愛知、日本  

開催期間： 2012年12月03日 - 2012年12月07日   記述言語：英語   開催地：San Francisco, CA, U.S.A.  

開催期間： 2012年11月12日 - 2012年11月14日   記述言語：英語   開催地：ookayama, Tokyo, Japan  

開催期間： 2012年10月20日 - 2012年10月23日   記述言語：日本語   開催地：札幌市、北海道、日本  

開催期間： 2012年10月20日 - 2012年10月23日   記述言語：日本語   開催地：札幌市、北海道、日本  

開催期間： 2012年10月20日 - 2012年10月23日   記述言語：日本語   開催地：札幌市、北海道、日本  

開催期間： 2012年10月20日 - 2012年10月23日   記述言語：日本語   開催地：札幌市、北海道、日本  

開催期間： 2012年10月01日   記述言語：日本語   開催地：立川市、東京、日本  

開催期間： 2012年09月19日   記述言語：日本語   開催地：名古屋市、愛知県、日本  

開催期間： 2012年08月23日 - 2012年08月24日   記述言語：日本語   開催地：小金井市、東京、日本  

開催期間： 2012年05月20日 - 2012年05月25日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2012年05月20日 - 2012年05月25日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2012年05月20日 - 2012年05月25日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2012年02月16日 - 2012年02月17日   記述言語：日本語   開催地：立川、東京、日本  

開催期間： 2011年12月05日 - 2011年12月09日   記述言語：英語   開催地：San Francisco, CA, USA  

開催期間： 2011年10月24日   記述言語：英語   開催地：Nagoya, Aichi, Japan  

開催期間： 2011年09月12日 - 2011年09月15日   記述言語：日本語   開催地：福岡、日本  

開催期間： 2011年08月03日 - 2011年08月04日   記述言語：日本語   開催地： 京都、日本  

開催期間： 2010年12月13日 - 2010年12月17日   記述言語：英語   開催地：San Francisco, CA, USA  

開催期間： 2010年10月01日   記述言語：日本語   開催地：那覇、沖縄、日本  

開催期間： 2009年09月01日   記述言語：日本語   開催地：金沢、石川、日本  

開催期間： 2009年09月01日   記述言語：日本語   開催地：金沢、石川、日本  

開催期間： 2008年06月16日 - 2008年06月20日   記述言語：英語   開催地：Busan, Korea  

開催期間： 2008年05月25日 - 2008年05月30日   記述言語：英語   開催地：幕張、千葉、日本  

開催期間： 2007年12月10日 - 2007年12月14日   記述言語：英語   開催地：San Francisco, CA, USA  

開催期間： 2007年10月23日 - 2007年10月27日   記述言語：英語   開催地：京都、日本  

開催期間： 2007年05月19日 - 2007年05月24日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2006年12月11日 - 2006年12月15日   記述言語：英語   開催地： San Francisco, CA, USA  

開催期間： 2006年11月04日 - 2006年11月07日   記述言語：日本語   開催地：相模原、神奈川、日本  

開催期間： 2006年05月14日 - 2006年05月18日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2006年05月14日 - 2006年05月18日   記述言語：日本語   開催地：幕張、千葉、日本  

開催期間： 2005年09月28日 - 2005年10月01日   記述言語：英語   開催地：京都、日本  

開催期間： 2005年08月04日 - 2005年08月05日   記述言語：日本語   開催地：東京、日本  

開催期間： 2021年12月13日 - 2021年12月17日   記述言語：英語   開催地： New Orleans, LA, USA & Online  

開催期間： 2021年12月13日 - 2021年12月17日   記述言語：英語   開催地： New Orleans, LA, USA & Online  

開催期間： 2021年12月13日 - 2021年12月17日   記述言語：英語   開催地： New Orleans, LA, USA & Online  

開催期間： 2021年12月13日 - 2021年12月17日   記述言語：英語   開催地： New Orleans, LA, USA & Online  

開催期間： 2021年12月13日 - 2021年12月17日   記述言語：英語   開催地： New Orleans, LA, USA & Online  

開催期間： 2021年10月31日 - 2021年11月04日   記述言語：日本語   開催地： Online  

開催期間： 2021年10月31日 - 2021年11月04日   記述言語：日本語   開催地： Online  

開催期間： 2021年10月31日 - 2021年11月04日   記述言語：日本語   開催地： Online  

開催期間： 2021年10月31日 - 2021年11月04日   記述言語：日本語   開催地： Online  

開催期間： 2021年10月31日 - 2021年11月04日   記述言語：日本語   開催地： Online  

開催期間： 2021年10月31日 - 2021年11月04日   記述言語：日本語   開催地： Online  

開催期間： 2021年10月31日 - 2021年11月04日   記述言語：日本語   開催地： Online  

開催期間： 2021年10月31日 - 2021年11月04日   記述言語：日本語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2021年05月30日 - 2021年06月06日   記述言語：英語   開催地： Online  

開催期間： 2019年07月28日 - 2019年08月02日   発表言語：英語   講演種別：招待講演   開催地：Suntec City, Singapore  

開催期間： 2019年07月28日 - 2019年08月02日   発表言語：英語   講演種別：招待講演   開催地：Suntec City, Singapore  

開催期間： 2019年07月28日 - 2019年08月02日   発表言語：英語   講演種別：招待講演   開催地：Suntec City, Singapore  

開催期間： 2019年06月02日 - 2019年06月07日   発表言語：英語   講演種別：招待講演   開催地：Fujiyoshida, Yamanashi  

開催期間： 2019年06月02日 - 2019年06月07日   発表言語：英語   講演種別：招待講演   開催地：Fujiyoshida, Yamanashi  

開催期間： 2018年12月10日 - 2018年12月14日   発表言語：英語   講演種別：招待講演   開催地：Washington, D.C., USA  

開催期間： 2018年12月10日 - 2018年12月14日   発表言語：英語   講演種別：招待講演   開催地：Washington, D.C., USA  

開催期間： 2018年11月23日 - 2018年11月27日   発表言語：日本語   講演種別：招待講演   開催地：名古屋、愛知、日本  

開催期間： 2018年11月23日 - 2018年11月27日   発表言語：日本語   講演種別：招待講演   開催地：名古屋、愛知、日本  

開催期間： 2018年11月23日 - 2018年11月27日   発表言語：日本語   講演種別：招待講演   開催地：名古屋、愛知、日本  

開催期間： 2018年11月23日 - 2018年11月27日   発表言語：日本語   講演種別：招待講演   開催地：名古屋、愛知、日本  

開催期間： 2018年05月20日 - 2018年05月24日   発表言語：日本語   講演種別：招待講演   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   発表言語：日本語   講演種別：招待講演   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   発表言語：日本語   講演種別：招待講演   開催地：幕張、千葉  

開催期間： 2018年05月20日 - 2018年05月24日   発表言語：日本語   講演種別：招待講演   開催地：幕張、千葉  

開催期間： 2017年12月11日 - 2017年12月15日   発表言語：英語   講演種別：招待講演   開催地：New Orleans, LA, USA  

開催期間： 2017年10月11日 - 2017年10月13日   発表言語：英語   講演種別：招待講演   開催地：Geomagnetic Observatory Niemegk, Germany  

開催期間： 2013年06月24日 - 2013年06月28日   発表言語：英語   講演種別：招待講演   開催地：Brisbene, Australia  

科目区分：学部専門科目