Faculty Profiles - SHINBORI Atsuki

Papers - SHINBORI Atsuki

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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 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 ) 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

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

Kozai M., Tanaka Y., Abe S., Minamiyama Y., Shinbori A., Kadokura A.

Data Science Journal Vol. 24 2025

Language：English Publishing type：Research paper (scientific journal) Publisher：Data Science Journal

The AMIDER, Advanced Multidisciplinary Integrated-Database for Exploring new Research, is a newly developed research data catalog to demonstrate an advanced database application. AMIDER is characterized as a multidisciplinary database equipped with a user-friendly web application. Its catalog view displays diverse research data at once beyond any limitation of each individual discipline. Some useful functions, such as a selectable data download, data format conversion, and display of data visual information, are also implemented. Further advanced functions, such as visualization of dataset mutual relationship, are also implemented as a preliminary trial. These characteristics and functions are expected to enhance the accessibility to individual research data, even from non-expert users, and be helpful for collaborations among diverse scientific fields beyond individual disciplines. Multidisciplinary data management is also one of AMIDER’s uniqueness, where various metadata schemas can be mapped to a uniform metadata table, and standardized and self-describing data formats are adopted. AMIDER website (https://amider.rois.ac.jp/) had been launched in April 2024. As of July 2024, over 15,000 metadata in various research fields of polar science have been registered in the database, and approximately 500 visitors are viewing the website every day on average. Expansion of the database to further multidisciplinary scientific fields, not only polar science, is planned, and advanced attempts, such as applying natural language processing (NLP) to metadata, have also been considered.

DOI： 10.5334/dsj-2025-007

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

Regional Ionospheric Super Bubble Induced by Significant Upward Plasma Drift During the 1 December 2023 Geomagnetic Storm Reviewed International coauthorship Open Access

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

Journal of Geophysical Research: Space Physics Vol. 129 ( 6 ) 2024.6

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

An unseasonal equatorial plasma bubble (EPB) event occurred in the East/Southeast Asian sector during the geomagnetic storm on 1 December 2023, causing strong amplitude scintillations from equatorial to middle latitudes. Based on the observations from multiple instruments over a large latitudinal and longitudinal region, the spatial features of the super EPB were investigated. The EPB developed vertically at a fast rising speed ∼470 m/s over the magnetic equator and extended to a very high middle latitude more than 40°N, despite that the storm intensity was not very strong with the minimum SYM-H index −132 nT. In the zonal direction, the super EPB covered over a specific region ∼95–140°E, where the local sunset roughly coincided with southward turning of interplanetary magnetic field (IMF) Bz component. Before the onset of the super EPB, significant upward plasma drift up to ∼110 m/s was observed over the magnetic equator, which could amplify the growth rate of Rayleigh-Taylor instability and lead to the generation of the super EPB. The significant drift was likely caused by eastward penetration electric field (PEF) due to sharp southward turning of IMF Bz. The local time of storm onset and duration of IMF Bz southward turning during the storm main phase may partly determine the onset region and zonal coverage of the EPB.

DOI： 10.1029/2024JA032430

Thermospheric Wind Response to March 2023 Storm: Largest Wind Ever Observed With a Fabry-Perot Interferometer in Tromsø, Norway Since 2009 Reviewed International coauthorship

Oyama, S; Vanhamäki, H; Cai, L; Shinbori, A; Hosokawa, K; Sakanoi, T; Shiokawa, K; Aikio, A; Virtanen, II; Ogawa, Y; Miyoshi, Y; Kurita, S; Nishitani, N

SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS Vol. 22 ( 3 ) 2024.3

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

Solar cycles 24–25 were quiet until a geomagnetic storm with a Sym-H index of −170 nT occurred in late March 2023. On March 23–24, a Fabry-Perot interferometer (FPI; 630 nm) in Tromsø, Norway, recorded the highest thermospheric wind speed of over 500 m/s since 2009. Comparisons with magnetometer readings in Scandinavia showed that a large amount of electromagnetic energy was transferred to the ionosphere-thermosphere system. Total electron content maps suggested an enlarged auroral oval and revealed that the FPI observed winds near the polar cap instead of inside the oval for a long period during the storm main phase. The FPI wind had a strong equatorward component during the storm, likely because of the powerful anti-sunward ionospheric plasma flow in the polar cap. The positive Y-component of the IMF for 6 days before the storm caused a successive westward component of the FPI-measured wind during the storm main phase. On March 24, the first day of the storm recovery phase, thermospheric wind disturbed and the ionospheric density decreased significantly at high latitudes. This density depression lasted for several days, and a large amount of electromagnetic energy during the storm modified the thermospheric dynamics and ionospheric plasma density.

DOI： 10.1029/2023SW003728

Performance of the double-thin-shell approach for studying nighttime medium-scale traveling ionospheric disturbances using two dense GNSS observation networks in Japan Reviewed

Fu, WZ; Otsuka, Y; Shinbori, A; Nishioka, M; Perwitasari, S

EARTH PLANETS AND SPACE Vol. 76 ( 1 ) 2024.1

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

Electrodynamic coupling between the ionospheric E and F regions is widely recognized as the underlying mechanism for generating medium-scale traveling ionospheric disturbances (MSTIDs) during nighttime at midlatitudes. Recently, the double-thin-shell approach has proven to be a useful tool for studying the E–F coupling. By using total electron content (TEC) measurements, this approach enables the simultaneous reconstruction of electron density perturbations in both the E and F regions with broad and continuous coverage. However, the current reconstruction performance is limited when using only GPS-TEC measurements from GEONET, a dense network of ground-based Global Navigation Satellite System (GNSS) receivers over Japan. The expansion of available data sources and the integration of multi-GNSS observation data are considered important to enhance the double-thin-shell model. Fortunately, SoftBank Corp., a Japanese telecommunications provider, has recently developed a dense independent GNSS observation network to improve positioning services. In this paper, we analyze the potential of the improved double-thin-shell approach and emphasize the importance of incorporating multi-GNSS observation data from both GEONET and SoftBank networks. The solvability analysis, simulation, and observation results collectively indicate a substantial improvement in the spatiotemporal resolution. Specifically, the longitudinal and latitudinal resolution is improved from 0.15° to 0.1° in the E region, and from 0.5° to 0.3° in the F region. The temporal resolution is also improved from 2 to 1 min. In addition, significant improvements have been achieved in the reconstruction performance, particularly for the E region under complex background conditions. Based on these assessments, we conclude that the incorporation of GEONET and SoftBank GNSS observation data holds significant potential for improving the double-thin-shell model and advancing our understanding of MSTIDs. Graphical abstract: [Figure not available: see fulltext.]

DOI： 10.1186/s40623-023-01956-8

Statistical Analysis of Global and Regional Ionospheric Total Electron Content (TEC) Using Extreme Value Distributions Reviewed International coauthorship

Emmela, S; Ratnam, DV; Otsuka, Y; Shinbori, A; Sori, T; Nishioka, M; Perwitasari, S

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING Vol. 62 page： 1 - 8 2024

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Geoscience and Remote Sensing

Satellite-based radio communication and navigation systems rely mostly on transionospheric propagation of radio signals concerning changes by total electron content (TEC). Therefore, it is necessary to understand the changing behavior of structural variations of ionospheric TEC for high-frequency applications besides mitigating the risks associated with the space weather impacts for navigation and aviation applications. The reference thresholds identified for moderate and severe levels of threshold activity for TEC by the International Civil Aviation Organization (ICAO) are 125 and 175 TECU, respectively. In view of this, statistical analysis of long-term ground-based global navigation satellite system (GNSS) TEC data of 25 years (1997-2021) using extreme value theory (EVT) is performed for both magnetically quiet and disturbed day conditions for four different regions - India (5-45°N), Japan low (20-30°N), Japan mid-latitudes (30-50°N), and global regions to identify the extreme ionospheric TEC events that take place once in 11, 22, 44, 66, 88, and 110 years with 95% confidence intervals. In the present work, both generalized extreme value (GEV) using annual maxima and generalized Pareto distribution (GPD) using peak-over-threshold (PoT) analysis are performed. A likelihood test and PoT constraint in addition to adjustment of shape parameter illustrate that GPD works better than GEV to identify return periods of extreme events. The recommended TEC moderate and severe thresholds for India, Japan low, Japan mid-latitude, and global regions are 121, 101, 90, and 139 TECU and 131, 135, 98, and 157 TECU, respectively. The analysis would be helpful in developing risk assessment and mitigation strategies for critical (GNSS) space weather systems.

DOI： 10.1109/TGRS.2023.3338513

A Survey on Databases of Specialized Fields and Research Data in Nagoya University Reviewed

NAOE Chizuko, NOSÉ Masahito, SHINBORI Atsuki, MIYOSHI Yoshizumi, HORI Tomoaki, HASHIBA Junko, OHIRA Tsukasa, GAKIYA Rui, OKAMOTO Maiko, SAGARA Takeshi

The Journal of Information Science and Technology Association Vol. 74 ( Special_Issue ) page： 2024-002 - 2024-002 2024

Multi-Instrument Observations of the Evolution of Polar Cap Patches Associated With Flow Shears and Particle Precipitation Reviewed International coauthorship

Zhang, D; Zhang, QH; Oksavik, K; Xing, ZY; Lyons, LR; Yang, HG; Li, GJ; Hosokawa, K; Shinbori, A; Ma, YZ; Wang, Y; Wang, XY

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 128 ( 12 ) 2023.12

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

Simultaneous observations from Defense Meteorological Satellite Program, Swarm, Resolute Bay all-sky imagers, GPS Total Electron Content and Super Dual Auroral Radar Network, are used to investigate the evolution and key characteristics of the Tongue of Ionization (TOI) being restructured into a polar cap patch. Six satellites crossed the TOI of patch as it moved from the dayside to the nightside. It was initially hot, then a mix of both cold and hot, and finally it became a cold patch. This suggests that cold patch is not only a result of solar extreme ultraviolet radiation, but may also develop when a hot patch cools down. Soft-electron precipitation and flow shears both contribute to the TOI restructuring and the appearance of polar cap patch. The plasma density of patch at ∼500 km was at least 4 times higher than at ∼800 km. The plasma density enhancement gradually decreased as the patch evolved due to decreased production and transport of cold nightside low-density plasma. Moreover, the duskward motion of the patch was influenced by changes in the ionospheric convection pattern.

DOI： 10.1029/2023JA032176

New aspects of the upper atmospheric disturbances caused by the explosive eruption of the 2022 Hunga Tonga–Hunga Ha’apai volcano Invited Reviewed

A. Shinbori, Y. Otsuka, T. Sori, M. Nishioka, S. Perwitasari, T. T. Tsuda, N. Nishitani, A. Kumamoto, F. Tsuchiya, S. Matsuda, Y. Kasahara, A. Matsuoka, S. Nakamura, Y. Miyoshi, I. Shinohara

Earth Planets Space Vol. 75 ( 1 ) page： 175 2023.11

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