Faculty Profiles - SHINBORI Atsuki

Papers - SHINBORI Atsuki

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Observational Evidence for the Nonlinear Growth of Chorus Waves Caused by Substorm Injected Energetic Electrons Reviewed International coauthorship

Chen, R; Miyoshi, Y; Zhao, H; Chen, HY; Wang, XY; Kasahara, Y; Matsuda, S; Hori, T; Tsuchiya, F; Kumamoto, A; Shinbori, A; Kasahara, S; Yokota, S; Keika, K; Mitani, T; Takashima, T; Matsuoka, A; Teramoto, M; Yamamoto, K; Shinohara, I

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 130 ( 7 ) 2025.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research Space Physics

Substorm energetic electron injections serve as a significant energy source for chorus wave generation, markedly altering the distribution of energetic electrons. Using the Arase satellite data, we present direct evidence for the nonlinear evolution of chorus waves following a substorm injection. The substorm injection causes the enhancement of energetic electron fluxes (∼20–200 keV) during which chorus waves appear as clear and intense rising-tone elements. Linear theoretical analysis shows that anisotropic energetic electrons provide free energy for the generation of seed chorus waves and the enhancement of energetic electrons increases the linear growth rate. Furthermore, nonlinear theoretical analysis shows that the increase in energetic electrons reduces the threshold amplitude, which is conducive to the chorus wave entering the nonlinear growth stage. These results indicate that nonlinear growth plays a significant role in the amplification and spectral evolution of chorus waves through a decrease in the threshold amplitudes.

DOI： 10.1029/2025JA033931

On the Extraordinary L‐Band Scintillation Event Observed in the American Sector During the 23–24 March 2023 Geomagnetic Storm Reviewed International coauthorship Open Access

J. Gomez Socola, F. S. Rodrigues, J. Sousasantos, M. R. Quesada, R. Heelis, Y. Otsuka, A. Shinbori, M. Nishioka, S. Perwitasari

Space Weather Vol. 23 ( 6 ) 2025.6

Strong ionospheric activity at the MWA site associated with plasma bubble measured by GNSS Reviewed International coauthorship

Yoshiura, S; Otsuka, Y; Trott, CM; Null, D; Nishitani, N; Takahashi, K; Nishioka, M; Perwitasari, S; Shinbori, A

PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN Vol. 77 ( 3 ) page： 556 - 561 2025.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Publications of the Astronomical Society of Japan

The Earth's ionosphere refracts radio signals, shifting the apparent position of radio sources. Wide-field measurements with a radio interferometercan measure the ionospheric distortion. The Murchison Widefield Array (MWA) has the ability to capture ionospheric structures that are smallerthan 100 km in extent. We report unusually strong ionospheric activity in MWA data during a magnetic storm on 2023 December 1. The duct-likestructure (roughly 50 km × >100 km) passes through the MWA field-of-view with a velocity of ∼100 m s<sup>-1</sup>. The offsets of the apparent positionof the radio source are more than 1° in the MWA observation data at around 180 MHz. By comparing the total electron content (TEC) dataobtained from the global navigation satellite systems' receiver network, we have found that the TEC fluctuations represented by a high rate ofTEC change index coincided with the strong ionospheric activity observed by the MWA. This result suggests that unusual ionospheric signaturesdetected by the MWA could be caused by plasma bubbles extending across Western Australia during a magnetic storm.

DOI： 10.1093/pasj/psaf024

Unveiling the vertical ionospheric responses following the 2024 Noto Peninsula Earthquake with an ultra-dense GNSS network Reviewed International coauthorship

Fu, WZ; Otsuka, Y; Ssessanga, N; Shinbori, A; Sori, T; Nishioka, M; Perwitasari, S

EARTH PLANETS AND SPACE Vol. 77 ( 1 ) 2025.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Earth Planets and Space

This paper leverages total electron content (TEC) perturbations obtained from an ultra-dense Global Navigation Satellite System (GNSS) receiver network across the Japanese archipelago to reconstruct the three-dimensional (3-D) structures of ionospheric responses following the 2024 Noto Peninsula Earthquake (Mw7.5). Reconstructions successfully captured the concentric electron density perturbations extending radially from the epicenter in the horizontal and vertical cross section 9–10 min after the earthquake. At south of the epicenter, in the meridional-vertical cross sections, phases of the electron density perturbations have a tilted structure stretching from north-up to south-down, which gradually becomes more vertical over time. Model calculations indicate that these electron density perturbations are caused by seismic acoustic waves, with sound velocity increasing at higher altitudes. However, the difference between theoretical predictions and reconstruction results may suggest the non-linear propagation of acoustic waves in the ionosphere, and the presence of multiple acoustic wave sources along the fault.

DOI： 10.1186/s40623-025-02211-y

A Peculiar Discontinuous Ionospheric Latitudinal Variation Over the East Asia Region During the Recovery Phase of the November 2003 Super Magnetic Storm: A Hint From May 2024 Superstorm Reviewed International coauthorship

Guo, X; Zhao, BQ; Yu, TT; Zhang, YL; Otsuka, Y; Shinbori, A; Nishioka, M; Perwitasari, S; Sun, WJ; Hu, LH; Li, GZ; Ren, ZP

GEOPHYSICAL RESEARCH LETTERS Vol. 52 ( 9 ) 2025.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Geophysical Research Letters

In this study, we analyze a discontinuous negative storm evolution process in the ionosphere over the East Asian region during the recovery phase of the geomagnetic storms on 20 and 21 November 2003, using data from the Global Ultraviolet Imager (GUVI) for [O] and [N<inf>2</inf>] column density ratio (Σ[O]/[N<inf>2</inf>]), Total Electron Content (TEC), as well as ionospheric parameters, namely, the ionospheric peak height (hmF2) and peak electron density (NmF2), supplemented by Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations. The event lasted 3–4 hr and may represent the first simultaneous observation of vortex-like structures in both the thermosphere and ionosphere since Solar Cycle 23. Our research findings suggest that this structure is most probably related to the vortex-like structure of thermospheric composition caused by thermospheric winds blowing from the Southern Hemisphere under the influence of pressure gradient force and Coriolis force.

DOI： 10.1029/2025GL114919

Arase In Situ Observations of High-Frequency Electromagnetic Ion Cyclotron (EMIC) Waves in Regions Close to the Earth During the May 2024 Storm Reviewed Open Access

Jun, CW; Miyoshi, Y; Hori, T; Kitamura, N; Kim, KH; Lee, JH; Bortnik, J; Lyons, L; Shinohara, I; Matsuoka, A; Kasahara, Y; Matsuda, S; Kasaba, Y; Teramoto, M; Yamamoto, K; Shinbori, A

GEOPHYSICAL RESEARCH LETTERS Vol. 52 ( 7 ) 2025.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Geophysical Research Letters

During the May 2024 storm, the minimum Dst index was approximately −412 nT, marking the largest geomagnetic storm of the past decade. This event caused the inner edge of the ring current to penetrate deeply into the inner magnetosphere during the main phase of the storm. We present observations of high-frequency electromagnetic ion cyclotron (HF EMIC) wave activity during this intense geomagnetic storm using data from the Arase satellite. Arase observations showed that HF EMIC waves with frequencies of 5–36 Hz at L ∼ 2, occurred mainly during the main and early-recovery phases. The minimum resonance energy of energetic protons and relativistic electrons associated with HF EMIC waves suggests their potential to cause the loss of relativistic electrons in the low L-shell region. Our observations provide new insights into the generation of EMIC waves and the dynamics of energetic particles at low L-shells in the inner magnetosphere.

DOI： 10.1029/2024GL112489

Characteristic E-Region Plasma Signature of Magnetospheric Wave-Particle Interactions Reviewed International journal Open Access

Magnus F. Ivarsen, Yukinaga Miyashita, Jean-Pierre St-Maurice, Glenn C. Hussey, Brian Pitzel, Draven Galeschuk, Saif Marei, Richard B. Horne, Yoshiya Kasahara, Shoya Matsuda, Satoshi Kasahara, Kunihiro Keika, Yoshizumi Miyoshi, Kazuhiro Yamamoto, Atsuki Shinbori, Devin R. Huyghebaert, Ayako Matsuoka, Shoichiro Yokota, Fuminori Tsuchiya

Physical Review Letters Vol. 134 ( 14 ) page： 145201 - 145201 2025.4

Language：English Publishing type：Research paper (scientific journal) Publisher：American Physical Society (APS)

Plasma waves in the magnetosphere scatter electrons, causing them to precipitate into Earth’s atmosphere, imparting their temporal characteristics to diffuse auroras. In a case study of conjugate radar and satellite observations, we demonstrate a close and unprecedented association between enhanced electrostatic cyclotron harmonic wave activity in the magnetosphere and the appearance of meter-scale plasma turbulence a few seconds later in the lower ionosphere on nearby magnetic field lines. Such direct structuring of the ionosphere carries implications for our understanding of space weather.

Published by the American Physical Society 2025

DOI： 10.1103/PhysRevLett.134.145201

Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.134.145201/fulltext

Enhancing PINE Model Performance through Database Extension

Sadaf Shahsavani, Yuri Y. Shprits, Stefano Bianco, Bernhard Haas, Artem Smirnov, Yoshiya Kasahara, Fuminori Tsuchiya, Atsushi Kumamoto, Atsuki Shinbori, Ayako Matsuoka, Mariko Teramoto, Kazuhiro Yamamoto, Iku Shinohara, Yoshizumi Miyoshi

2025.3

Satellite observations and modeling of the plasmapause structure and dynamics Reviewed International coauthorship Open Access

Shigeto Watanabe, Dieter Bilitza, Fuminori Tsuchiya, Atsushi Kumamoto, Yoshizumi Miyoshi, Yoshiya Kasahara, Tomoaki Hori, Atsuki Shinbori, Ayako Matsuoka, Iku Shinohara

Advances in Space Research Vol. 75 ( 5 ) page： 4230 - 4244 2025.3

Language：English Publishing type：Research paper (scientific journal)

We investigated the structure and dynamics of the plasmapause using electron density data from the Arase (ERG) satellite between 2017 and 2019. By fitting the electron density profile to a hyperbolic function using the least-squares method, 1891 plasmapause events were identified. The hyperbolic function's fitting parameters were used to estimate the plasmapause's location and thickness. The plasmapause location and thickness were mapped onto the geomagnetic equator plane. We examined the dependence of the plasmapause location and thickness on the geomagnetic disturbance. The median plasmapause location on the geomagnetic equator plane was 32,089 km from Earth's center. Plasmapause locations depend on geomagnetic disturbances that vary between four and six radii of the Earth. In contrast, the median plasmapause thickness obtained by fitting a hyperbolic function on the geomagnetic equator plane was 2472 km. The thickness changed from ∼1500 km at night to ∼ 3000 km during the daytime. The thickness was several times larger than the ring current H+ Larmor radius, suggesting an association with plasma instability in the plasmapause due to the penetration of magnetospheric electric fields. Additionally, we developed a three-dimensional empirical electron density model with historical effects associated with refilling the plasmasphere, plasmapause, and magnetosphere. The International Reference Ionosphere (IRI) model can be enhanced to incorporate the electron density model of the plasmasphere and estimate the total electron content (TECp) in the plasmasphere using the empirical model. Our analysis provides valuable insights into plasmapause and contributes to a better understanding of the inner magnetosphere.

DOI： 10.1016/j.asr.2024.10.015

Statistical Survey of Loss Cone Electrons Observed In Situ in the Inner Magnetosphere Reviewed Open Access

R. Takahara, I. Shinohara, S. Kasahara, K. Asamura, S. Yokota, K. Keika, Y. Kazama, S.‐Y. Wang, S. W. Y. Tam, T.‐F. Chang, B.‐J. Wang, C.‐W. Jun, T. Hori, A. Matsuoka, M. Teramoto, K. Yamamoto, Y. Kasahara, S. Matsuda, A. Kumamoto, A. Shinbori, F. Tsuchiya, Y. Miyoshi

Geophysical Research Letters Vol. 52 ( 3 ) 2025.2

Language：English Publishing type：Research paper (scientific journal) Publisher：American Geophysical Union (AGU)

Abstract

We report a statistical result of electrons inside the loss cone with energies of 67 eV–88 keV using electron measurements obtained in situ by the Arase satellite in the inner magnetosphere around the magnetic equator for 60 months. Loss cone electrons are found with a high occurrence probability from the nightside to the dawnside at approximately L = 6. For 641 eV–88 keV electrons, the high‐occurrence region shifts toward later magnetic local times (MLTs) with increasing loss cone electron energy. The spatial distribution of the occurrence probability around MLT = 22–3 at L = 5–6 is consistent with the calculated average resonance energy distribution of whistler mode chorus waves near the magnetic equator. These results suggest that pitch angle scattering driven by chorus waves plays the main role in electron precipitation in this region.

DOI： 10.1029/2024GL112948

Multi‐Event Analysis of STEVE, SAR Arc, and Red/Green Arc at Subauroral Latitudes Using Data From Ground Optical and Radio Instruments and the Arase and Van Allen Probes Satellites Reviewed Open Access

Rei Sugimura, Kazuo Shiokawa, Yuichi Otsuka, Shin‐ichiro Oyama, Arto Oksanen, Martin Connors, Akira Kadokura, Igor Poddelsky, Nozomu Nishitani, Simon G. Shepherd, J. Michael Ruohoniemi, Charles Smith, Harlan Spence, Geoff Reeves, Herbert O. Funsten, Yoshizumi Miyoshi, Iku Shinohara, Yoshiya Kasahara, Fuminori Tsuchiya, Atsushi Kumamoto, Atsuki Shinbori, Kazushi Asamura, Shoichiro Yokota, Yoichi Kazama, C.‐W. Jun, Shiang‐Yu Wang, Sunny W. Y. Tam, Tzu‐Fang Chang, Bo‐Jhou Wang, Satoshi Kasahara, Kunihiro Keika, Tomoaki Hori, Ayako Matsuoka

Journal of Geophysical Research: Space Physics Vol. 130 ( 2 ) 2025.2

Language：English Publishing type：Research paper (scientific journal) Publisher：American Geophysical Union (AGU)

Abstract

Strong Thermal Emission Velocity Enhancement (STEVE) is a latitudinally narrow, purple‐band emission observed at subauroral latitudes. Stable Auroral Red (SAR) arcs characterized by major red emission, and red/green arcs with both red and green emissions also occur at subauroral latitudes. Characteristics of magnetospheric source plasma and electromagnetic fields of these three types of arcs have not been fully understood because of the limited conjugate observations between magnetosphere and the ground. In this study, we report 11 conjugate observations (2 STEVEs, 7 SAR arcs, and 2 red/green arcs), using all‐sky images obtained at seven ground stations over more than four years from January 2017 to April 2021 and magnetospheric satellites (Arase and Van Allen Probes). We found that, in the inner magnetosphere, the source region of STEVEs and red/green arcs were located outside the plasmasphere, and that of the SAR arc was in the region of spatial overlap between the plasmasphere and ring current region. Electromagnetic waves at frequencies below 1 Hz were observed for STEVEs and red/green arcs. SuperDARN radar data showed a strong westward plasma flow in the ionosphere, especially during STEVE events, whereas the plasma flows associated with SAR arcs and red/green arcs were generally weaker and variable. The STEVE and SAR arc can appear simultaneously at slightly different latitudes and STEVEs and red/green arcs can transform into SAR arcs. These first comprehensive ground‐satellite measurements of three types of subauroral‐latitude auroras increase our understanding on similarlity, differences, and coupling of these auroras in the ionosphere and the magnetosphere.

DOI： 10.1029/2024JA032793

The Solar and Geomagnetic Storms in May 2024: A Flash Data Report Reviewed Open Access

Hisashi Hayakawa, Yusuke Ebihara, Alexander Mishev, Sergey Koldobskiy, Kanya Kusano, Sabrina Bechet, Seiji Yashiro, Kazumasa Iwai, Atsuki Shinbori, Kalevi Mursula, Fusa Miyake, Daikou Shiota, Marcos V. D. Silveira, Robert Stuart, Denny M. Oliveira, Sachiko Akiyama, Kouji Ohnishi, Yoshizumi Miyoshi

Vol. 979 ( 1 ) 2025.1

Language：English Publishing type：Research paper (scientific journal)

In May 2024, the scientific community observed intense solar eruptions that
resulted in an extreme geomagnetic storm and auroral extension, highlighting
the need to document and quantify these events. This study mainly focuses on
their quantification. The source active region (AR 13664) evolved from 113 to
2761 millionths of the solar hemisphere between 4 May and 14 May 2024. AR
13664's magnetic free energy surpassed 1033 erg on 7 May 2024, triggering 12
X-class flares. Multiple interplanetary coronal mass ejections (ICMEs) came out
from this AR, accelerating solar energetic particles toward Earth. At least
four ICMEs seemingly piled up to disturb the interplanetary space, according to
the satellite data and interplanetary scintillation data. The shock arrival at
17:05 UT on 10 May 2024 significantly compressed the magnetosphere down to ~
5.04 R_E, and triggered a deep Forbush decrease. GOES satellite data and
ground-based neutron monitors confirmed a ground-level enhancement from 2 UT to
10 UT on 11 May 2024. The ICMEs induced extreme geomagnetic storms, peaking at
a Dst index of -412 nT at 2 UT on 11 May 2024, marking the sixth-largest storm
since 1957. The AE and AL indices showed extreme auroral extensions that
located the AE/AL stations into the polar cap. We gathered auroral records at
that time and reconstructed the equatorward boundary of the visual auroral oval
to 29.8{\deg} invariant latitude. We compared naked-eye and camera auroral
visibility, providing critical caveats on their difference. We also confirmed
global enhancements of storm-enhanced density of the ionosphere.

DOI： 10.3847/1538-4357/ad9335

Other Link： http://arxiv.org/pdf/2407.07665v1

AMIDER: A Multidisciplinary Research Database and Its Application to Promote Open Science. Reviewed Open Access

Masayoshi Kozai, Yoshimasa Tanaka, Shuji Abe, Yasuyuki Minamiyama, Atsuki Shinbori, Akira Kadokura

Data Sci. J. Vol. 24 2025

Observations and statistical studies of orbit-driven plasma waves in low earth orbit at very low frequencies Reviewed

Hughes J., Collett I., Nasr C., Newheart A., Kelly R., Thaller S., Patel R., Johnstone C., Vance E., Wang H., Re N., Tatman B., Kasahara Y., Matsuda S., Kumamoto A., Tsuchiya F., Hori T., Shinbori A., Matsuoka A., Teramoto M., Yamamoto K., Miyoshi Y., Shinohara I.

Advances in Space Research 2025

Language：English Publishing type：Research paper (scientific journal) Publisher：Advances in Space Research

The number of resident space objects (RSOs), including debris and inactive satellites, is rapidly increasing, posing a growing threat to operational spacecraft. Additionally, many of these RSOs are too small to be reliably tracked by current radars. A novel solution to this problem is to use the disturbances in the plasma environment to track these objects. Over the last decade, theoretical, numerical, laboratory, and observational efforts have studied the generation and propagation of these disturbances. This study investigates these disturbances statistically using 5 months of Very Low Frequency (VLF) Electric (E) field data collected by the Arase satellite. This represents the first large-scale statistical observational study of RSO-generated waves. Specifically, we use E field power between 1 and 20 kHz from the Onboard Frequency Analyzer, which is part of the Plasma Wave Experiment (PWE) onboard the Arase satellite. We analyze this dataset by comparing the power between an “experiment” population of measurements taken where Arase was in a situation where RSO-generated waves would be observed, and a “control” population where Arase was in a situation where no RSO-generated waves would be observed. For robust comparisons, the two populations should have similar distributions of latitude, longitude, altitude, and time. However, rigidly enforcing this matching results in very small sample sizes. We therefore use three different approaches to this balancing. Our strongest results have a p-value of 1.3e-5, indicating that there is a less than 1 in 77,000 chance that the experiment and control populations are drawn from the same parent population. We take this as strong statistical evidence of RSO-generated waves. These encouraging results bolster the feasibility of using these waves as part of a future detection, identification, and tracking system.

DOI： 10.1016/j.asr.2025.07.013

Midlatitude Plasma Blob-like Structures Along With Super Equatorial Plasma Bubbles During the May 2024 Great Geomagnetic Storm Reviewed International coauthorship Open Access

Wenjie Sun, Guozhu Li, Biqiang Zhao, Shun Rong Zhang, Yuichi Otsuka, Lianhuan Hu, Guofeng Dai, Xiukuan Zhao, Haiyong Xie, Yi Li, Jianfei Liu, Yu Li, Baiqi Ning, Libo Liu, Atsuki Shinbori, Michi Nishioka, Septi Perwitasari

Geophysical Research Letters Vol. 51 ( 21 ) 2024.11

Language：English Publishing type：Research paper (scientific journal)

Plasma blob is generally a low-latitude phenomenon occurring at the poleward edge of equatorial plasma bubble (EPB) during post-sunset periods. Here we report a case of midlatitude ionospheric plasma blob-like structures occurring along with super EPBs over East Asia around sunrise during the May 2024 great geomagnetic storm. Interestingly, the blob-like structures appeared at both the poleward and westward edges of EPBs, reached up to 40°N magnetic latitudes, and migrated westward several thousand kilometers together with the bubble. The total electron content (TEC) inside the blob-like structures was enhanced by ∼50 TEC units relative to the ambient ionosphere. The blob-like structure at the EPB poleward edge could be partly linked with field-aligned plasma accumulation due to poleward development of bubble. For the blob-like structure at the EPB west side, one possible mechanism is that it was formed and enhanced accompanying the bubble evolution and westward drift.

DOI： 10.1029/2024GL111638

Monitoring of Ionospheric Variability Using the Low lAtitude Long Range Ionospheric raDar (LARID): Capabilities, Advantages and Limitations Reviewed International coauthorship Open Access

Wenjie Sun, Guozhu Li, Baiqi Ning, Lianhuan Hu, Yuichi Otsuka, Guofeng Dai, Haiyong Xie, Xiukuan Zhao, Yi Li, Atsuki Shinbori, Michi Nishioka, Septi Perwitasari, Chi Wang

Space Weather Vol. 22 ( 11 ) 2024.11

Language：English Publishing type：Research paper (scientific journal)

A Low lAtitude long Range Ionospheric raDar (LARID), which was built recently at Dongfang (19.2°N, 108.8°E, magnetic latitude 13.9°), Hainan Is., China, is employed to study the ionospheric variability over a large region. The LARID consists of two high frequency (HF) coherent backscatter radars, looking toward east and west, respectively, with a field-of-view covering a wide longitude from Africa to Pacific. Here we report some results by the LARID, with main focus on its capabilities, advantages and limitations in monitoring ionospheric variability. The results show that the LARID can detect various ionospheric variations at low latitudes, including (a) sequentially generated equatorial plasma bubbles over a longitude span of ∼80°, (b) near-range E region irregularities drifting across more than 1,000 km, (c) ionospheric background information retrieved from ground scatters, (d) traveling ionospheric disturbances, and (e) sporadic E structures reflecting HF radio waves at low elevation angles. It is demonstrated that the LARID provides an important tool for investigating different types of ionospheric variability over a broad region, especially over the Indian Ocean and west Pacific, and will contribute significantly to the regional ionospheric weather forecasting.

DOI： 10.1029/2024SW004134

Enhancing accessibility of research data through metadata conversion and registration in institutional repositories: Practices in the field of Solar-Terrestrial Physics Open Access

Masahito NOSÉ, Atsuki SHINBORI, Yoshizumi MIYOSHI, Tomoaki HORI, Tsukasa OOHIRA, Maiko OKAMOTO, Chizuko NAOE, Rui GAKIYA, Sachie TANAKA, Takeshi SAGARA, Takaaki AOKI, Shigeki MATSUBARA, Ichiro TAKAHASHI, Hidekazu HAYASHI, Kazunari YAMADA, Yasuyuki MINAMIYAMA, Yoshimasa TANAKA, Yasuo SAITO, Shuji ABE, Satoru UENO, Shun IMAJO, Takuya ASHIKITA, Yuko HORI, Toshiyuki SHIMIZU, Nanako OKAMURA, Kaoru HIRANO

The Journal of Information Science and Technology Association Vol. 74 ( 11 ) page： 487 - 493 2024.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Information Science and Technology Association, Japan

<p>The “Inter-university Upper atmosphere Global Observation NETwork (IUGONET)” project has developed a metadata database for ground-based observation data in Solar-Terrestrial Physics. In order to make this metadata database accessible to a wide range of research communities and the general public, we converted metadata in different metadata schema and registered them in academic institutional repositories. As a result, through regular harvesting between databases, the metadata has also been registered in the Institutional Repositories Database (IRDB), the Data Catalog Cross-Search System, and Google’s Dataset Search, significantly enhancing the visibility and accessibility of research data. Furthermore, effective metadata management was implemented in response to research metadata maintenance requests from policy-making bodies.</p>

DOI： 10.18919/jkg.74.11_487

X-Raying Neutral Density Disturbances in the Mesosphere and Lower Thermosphere Induced by the 2022 Hunga-Tonga Volcano Eruption-Explosion Reviewed Open Access

Satoru Katsuda, Hiroyuki Shinagawa, Hitoshi Fujiwara, Hidekatsu Jin, Yasunobu Miyoshi, Yoshizumi Miyoshi, Yuko Motizuki, Motoki Nakajima, Kazuhiro Nakazawa, Kumiko K. Nobukawa, Yuichi Otsuka, Atsushi Shinbori, Takuya Sori, Chihiro Tao, Makoto S. Tashiro, Yuuki Wada, Takaya Yamawaki

Geophysical Research Letters Vol. 51 ( 20 ) 2024.10

Language：English Publishing type：Research paper (scientific journal)

We present X-ray observations of the upper atmospheric density disturbance caused by the explosive eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano on 15 January 2022. From 14 January to 16 January, the Chinese X-ray astronomy satellite, Insight-HXMT, was observing the supernova remnant Cassiopeia A. The X-ray data obtained during Earth's atmospheric occultations allowed us to measure neutral densities in the altitude range of (Formula presented.) 90–150 km. The density profiles above 110 km altitude obtained before the major eruption are in reasonable agreement with expectations by both GAIA and NRLMSIS 2.0 models. In contrast, after the HTHH eruption, a severe density depletion was found up to 1,000 km away from the epicenter, and a relatively weak depletion extending up to (Formula presented.) km for over 8 hr after the eruption. In addition, density profiles showed wavy structures with a typical length scale of either (Formula presented.) 20 km (vertical) or (Formula presented.) 1,000 km (horizontal). This may be caused by Lamb waves or gravity waves triggered by the volcanic eruption.

DOI： 10.1029/2024GL112025

Enhancing Findability and Searchability of Research Data: Metadata Conversion and Registration in Institutional Repositories Reviewed International coauthorship Open Access

Masahito Nosé, Atsuki Shinbori, Yoshizumi Miyoshi, Tomoaki Hori, Tsukasa Ohira, Junko Hashiba, Chizuko Naoe, Rui Gakiya, Maiko Okamoto, Takeshi Sagara, Takaaki Aoki, Shigeki Matsubara, Ichiro Takahashi, Hidekazu Hayashi, Kazunari Yamada, Yasuyuki Minamiyama, Yoshimasa Tanaka, Shuji Abe, Satoru UeNo, Shun Imajo, Yasuo Saito, Takuya Ashikita, Yuko Hori, Toshiyuki Shimizu, Nanako Okamura, Kaoru Hirano, Lee Bargatze

Data Science Journal Vol. 23 2024.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Ubiquity Press, Ltd.

This paper outlines our practice to enhance the findability and searchability of research data through metadata conversion from the Space Physics Archive Search and Extract (SPASE) schema to a more generic schema, the Japan Consortium for Open Access Repository (JPCOAR) schema, and registration of converted metadata in institutional repositories. Traditionally, earth and space science research data have been organized using the SPASE schema. Although the SPASE schema is comprehensive, its usage has been restricted to highly professional databases, limiting broader accessibility and impeding cross-disciplinary research. We discuss a case study at Nagoya University where 284 metadata records were converted from SPASE to JPCOAR, and illustrate the process and benefits of this conversion. This approach significantly improved the visibility and usability of metadata across various platforms like the Institutional Repositories DataBase (IRDB), the Data Catalog Cross-Search System, and Google’s Dataset Search, extending access to a wider range of users beyond the highly professional scientific community. This approach also aligns with national policies in Japan on research data management and simplifies metadata handling for researchers. Future direction includes expanding this conversion and registration model to other universities and institutions by leveraging the ubiquity of the SPASE schema in the earth and space science fields. Our practice may be useful in other research fields. This initiative aims to improve the overall findability of research data, to foster cross-disciplinary collaboration, and to enhance the value of research data itself and of creators and managers of the data.

DOI： 10.5334/dsj-2024-040

Solar activity dependence for the relationship between nighttime medium-scale traveling ionospheric disturbance and sporadic E (Es) layer activities in summer during 1998–2019 over Japan Reviewed International coauthorship Open Access

Veera Kumar Maheswaran, Yuichi Otsuka, James A. Baskaradas, Venkata Ratnam Devanaboyina, Sriram Subramanian, Atsuki Shinbori, Takuya Sori, Michi Nishioka, Septi Perwitasari

Earth, Planets and Space Vol. 76 ( 1 ) 2024.6

Language：English Publishing type：Research paper (scientific journal)

To investigate solar activity dependence of the coupling between medium-scale traveling ionosphere disturbance (MSTID) and sporadic E (Es) layer, we analyzed the total electron content (TEC) obtained from a Japanese global positioning system (GPS) receivers and ionosonde at Kokubunji (35.7° N, 139.5° E) in Japan during the summer period of May–August from 1998 to 2019. To obtain perturbation TEC caused by MSTIDs, the detrended TEC is calculated by subtracting 1-h moving averages from the measured TEC for each pair of GPS satellite and receiver. The detrended TEC data are mapped on to the geographical coordinates to make detrended 2-D maps with spatial resolution of 0.15° × 0.15° in longitude and latitude. The MSTID activity is defined as a ratio of the standard deviation to the background TEC over Kokubunji in Japan. Day-to-day variations of the MSTID activity during summer nights was compared to Es layer parameters [critical frequency (foEs) and Δfo-b≡foEs-fbE, where fbEs is blanketing frequency] derived from ionosonde station at Kokubunji. We have found that the correlation coefficient between the MSTID activity and foEs(Δfo-b) between 1998 and 2019 is 0.5 3 (0.46) on average, suggesting that there is an electrodynamical coupling between the Es layer and F region could generate nighttime MSTIDs. We also have found that the correlation coefficient positively correlates with solar activity. This finding indicates that in the high solar activity conditions, when the growth rate of Perkins instability is relatively low, generation of the polarization electric fields in the Es layer could play a more important role to grow MSTIDs than in the low solar activity conditions. Graphical Abstract: (Figure presented.)

DOI： 10.1186/s40623-024-02023-6

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