研究者詳細 - 新堀　淳樹

論文 - 新堀　淳樹

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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 査読有り 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 52 巻 ( 7 ) 2025年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

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 134 巻 ( 14 ) 2025年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.134.145201/fulltext

Satellite observations and modeling of the plasmapause structure and dynamics 査読有り国際共著 Open Access

Watanabe, S; Bilitza, D; Tsuchiya, F; Kumamoto, A; Miyoshi, Y; Kasahara, Y; Hori, T; Shinbori, A; Matsuoka, A; Shinohara, I

ADVANCES IN SPACE RESEARCH 75 巻 ( 5 ) 頁： 4230 - 4244 2025年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Advances in Space Research

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 査読有り Open Access

Takahara, R; Shinohara, I; Kasahara, S; Asamura, K; Yokota, S; Keika, K; Kazama, Y; Wang, SY; Tam, SWY; Chang, TF; Wang, BJ; Jun, CW; Hori, T; Matsuoka, A; Teramoto, M; Yamamoto, K; Kasahara, Y; Matsuda, S; Kumamoto, A; Shinbori, A; Tsuchiya, F; Miyoshi, Y

GEOPHYSICAL RESEARCH LETTERS 52 巻 ( 3 ) 2025年2月

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 査読有り Open Access

Sugimura, R; Shiokawa, K; Otsuka, Y; Oyama, S; Oksanen, A; Connors, M; Kadokura, A; Poddelsky, I; Nishitani, N; Shepherd, SG; Ruohoniemi, JM; Smith, C; Spence, H; Reeves, G; Funsten, HO; Miyoshi, Y; Shinohara, I; Kasahara, Y; Tsuchiya, F; Kumamoto, A; Shinbori, A; Asamura, K; Yokota, S; Kazama, Y; Jun, CW; Wang, SY; Tam, SWY; Chang, TF; Wang, BJ; Kasahara, S; Keika, K; Hori, T; Matsuoka, A

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 130 巻 ( 2 ) 2025年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Geophysical Research: Space Physics

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 2024 May: A Flash Data Report 査読有り Open Access

Hayakawa, H; Ebihara, Y; Mishev, A; Koldobskiy, S; Kusano, K; Bechet, S; Yashiro, S; Iwai, K; Shinbori, A; Mursula, K; Miyake, F; Shiota, D; Silveira, MVD; Stuart, R; Oliveira, DM; Akiyama, S; Ohnishi, K; Ledvina, V; Miyoshi, Y

ASTROPHYSICAL JOURNAL 979 巻 ( 1 ) 2025年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Astrophysical Journal

In 2024 May, the scientific community observed intense solar eruptions that resulted in a great geomagnetic storm and auroral extensions, highlighting the need to document and quantify these events. This study mainly focuses on their quantification. The source active region (AR; NOAA Active Region 13664) evolved from 113 to 2761 millionths of the solar hemisphere between May 4 and 14. NOAA AR 13664’s magnetic free energy surpassed 1033 erg on May 7, triggering 12 X-class flares on May 8-15. Multiple interplanetary coronal mass ejections (ICMEs) were produced from this AR, accelerating solar energetic particles toward Earth. According to satellite and interplanetary scintillation data, at least four ICMEs erupted from AR 13664, eventually overcoming and combining each other. The shock arrival at 17:05 UT on May 10 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 2024 May 11. The ICMEs induced exceptional geomagnetic storms, peaking at a provisional Dst index of −412 nT at 2 UT on May 11, marking the sixth-largest storm since 1957. The AE and AL indices showed great 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 invariant latitude. We compared naked-eye and camera auroral visibility, providing critical caveats on their difference. We also confirmed global disturbances of the storm-enhanced density of the ionosphere.

DOI： 10.3847/1538-4357/ad9335

その他リンク： http://arxiv.org/pdf/2407.07665v1

AMIDER: A Multidisciplinary Research Database and Its Application to Promote Open Science 査読有り Open Access

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

Data Science Journal 24 巻 2025年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り国際共著 Open Access

Sun, WJ; Li, GZ; Zhao, BQ; Zhang, SR; Otsuka, Y; Hu, LH; Dai, GF; Zhao, XK; Xie, HY; Li, Y; Liu, JF; Li, Y; Ning, BQ; Liu, LB; Shinbori, A; Nishioka, M; Perwitasari, S

GEOPHYSICAL RESEARCH LETTERS 51 巻 ( 21 ) 2024年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geophysical Research Letters

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 査読有り国際共著 Open Access

Sun, WJ; Li, GZ; Ning, BQ; Hu, LH; Otsuka, Y; Dai, GF; Xie, HY; Zhao, XK; Li, Y; Shinbori, A; Nishioka, M; Perwitasari, S; Wang, C

SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS 22 巻 ( 11 ) 2024年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Space Weather

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

研究データをより見つけやすくするためのメタデータ変換と学術機関リポジトリへの登録：太陽地球系物理学分野における実践 Open Access

能勢正仁, 新堀淳樹, 三好由純, 堀智昭, 大平司, 岡本麻衣子, 直江千寿子, 我喜屋累, 田中幸恵, 相良毅, 青木学聡, 松原茂樹, 高橋一郎, 林秀和, 山田一成, 南山泰之, 田中良昌, 阿部修司, 上野悟, 今城峻, 齊藤泰雄, 芦北卓也, 堀優子, 清水敏之, 岡村奈々子, 平野かおる

情報の科学と技術 74 巻 ( 11 ) 頁： 487 - 493 2024年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人情報科学技術協会

<p>「超高層大気長期変動の全球地上ネットワーク観測・研究（IUGONET）」プロジェクトでは，太陽地球系物理学における地上観測データのメタデータデータベースを構築している。このメタデータデータベースを，幅広い研究コミュニティや一般市民が利用できるように，メタデータスキーマの変換を行い，学術機関リポジトリに登録した。その結果，データベース間の定期的なハーベストにより，学術機関リポジトリデータベース（IRDB），データカタログ横断検索システム，Google Dataset Searchなどにも登録され，研究データの可視性や到達可能性が大きく高まることとなった。また，政策決定機関からの研究メタデータ整備要求に対して，効果的なメタデータマネジメントを実施できた。</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 査読有り Open Access

Katsuda, S; Shinagawa, H; Fujiwara, H; Jin, HDKT; Miyoshi, Y; Miyoshi, Y; Motizuki, Y; Nakajima, M; Nakazawa, K; Nobukawa, KK; Otsuka, Y; Shinbori, A; Sori, T; Tao, CHR; Tashiro, MS; Wada, Y; Yamawaki, T

GEOPHYSICAL RESEARCH LETTERS 51 巻 ( 20 ) 2024年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geophysical Research Letters

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 査読有り国際共著 Open Access

Nosé M., Shinbori A., Miyoshi Y., Hori T., Ohira T., Hashiba J., Naoe C., Gakiya R., Okamoto M., Sagara T., Aoki T., Matsubara S., Takahashi I., Hayashi H., Yamada K., Minamiyama Y., Tanaka Y., Abe S., Ueno S., Imajo S., Saito Y., Ashikita T., Hori Y., Shimizu T., Okamura N., Hirano K., Bargatze L.

Data Science Journal 23 巻 2024年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Data Science Journal

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 (<i>Es</i>) layer activities in summer during 1998-2019 over Japan 査読有り国際共著 Open Access

Maheswaran, VK; Otsuka, Y; Baskaradas, JA; Devanaboyina, VR; Subramanian, S; Shinbori, A; Sori, T; Nishioka, M; Perwitasari, S

EARTH PLANETS AND SPACE 76 巻 ( 1 ) 2024年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Earth, Planets and Space

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 査読有り国際共著 Open Access

Sun, WJ; Li, GZ; Zhang, SR; Hu, LH; Dai, GF; Zhao, BQ; Otsuka, Y; Zhao, XK; Xie, HY; Li, Y; Ning, BQ; Liu, LB; Shinbori, A; Nishioka, M; Perwitasari, S

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 129 巻 ( 6 ) 2024年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Geophysical Research: Space Physics

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 査読有り国際共著

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 22 巻 ( 3 ) 2024年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

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

EARTH PLANETS AND SPACE 76 巻 ( 1 ) 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り国際共著

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

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 62 巻頁： 1 - 8 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

名古屋大学における専門分野のデータベース・研究データ調査査読有り

直江千寿子, 能勢正仁, 新堀淳樹, 三好由純, 堀智昭, 端場純子, 大平司, 我喜屋累, 岡本麻衣子, 相良毅

情報の科学と技術 74 巻 ( Special_Issue ) 頁： 2024-002 - 2024-002 2024年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人情報科学技術協会

<p>オープンサイエンスの推進には研究データの共有が不可欠であり，分野を超えて研究データを検索・再利用できるような仕組み（メタデータ整備）がますます重要になってきている。しかし，これまで各分野で扱っている研究データの特徴やメタデータの形式（メタデータスキーマ）について調査されたものはほとんどなく，その全容は明らかにされてこなかった。今回，名古屋大学の研究者を対象に調査を実施した。回答者数は221名と少なかったものの，分野を問わず広く研究データが公開・利用されていることと，10を超えるメタデータスキーマが学内で用いられていることが明らかになった。</p>

DOI： 10.18919/jkg.2024-002

Multi-Instrument Observations of the Evolution of Polar Cap Patches Associated With Flow Shears and Particle Precipitation 査読有り国際共著

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 128 巻 ( 12 ) 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 招待有り査読有り

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

EARTH PLANETS AND SPACE 75 巻 ( 1 ) 頁： 175 2023年11月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Earth, Planets and Space

The Hunga Tonga–Hunga Ha’apai (HTHH) undersea volcanic eruption that occurred at 04:15 UT on 15 January 2022 is one of the most explosive events in the modern era, and a vertical plume reached approximately 55 km, corresponding to a height of the lower mesosphere. The intense explosion and subsequent plume generated acoustic and atmospheric gravity waves detected by ground-based instruments worldwide. Because a global-scale atmospheric and ionospheric response to the large volcanic eruption has not yet been observed, it provides a unique opportunity to promote interdisciplinary studies of coupling processes in lithosphere–atmosphere–ionosphere with ground-based and satellite observations and modeling. Further, this event allows us to elucidate the propagation and occurrence features of traveling ionospheric disturbances, the generation of equatorial plasma bubbles, the cause of electron density holes around the volcano, and the magnetic conjugacy of magnetic field perturbations. The most notable point among these studies is that the medium-scale travelling traveling ionospheric disturbances (MSTIDs) have magnetic conjugacy even in the daytime ionosphere and are generated by an external electric field, such as an E-region dynamo field, due to the motions of neutrals in the thermosphere. This advocates a new generation mechanism of MSTIDs other than the neutral oscillation associated with atmospheric gravity waves and electrified MSTIDs, which are frequently observed during daytime and nighttime, respectively. This paper reviews the recent studies of atmospheric and ionospheric disturbances after the HTHH volcanic eruption and summarizes what we know from this extreme event analysis. Further, we analyzed new datasets not shown in previous studies to give some new insights to understanding of some related phenomena. As a result, we also found that 4-min plasma flow oscillations caused by the acoustic resonance appeared with the amplitude of approximately 30 m/s in the northern hemisphere a few hours before the initial arrival of the air pressure waves. The propagation direction was westward, which is the same as that of the daytime MSTIDs with a magnetic conjugate feature. This result suggests that the 4-min oscillations are generated by an external electric field transmitted to the northern hemisphere along magnetic field lines. Graphical Abstract: [Figure not available: see fulltext.].

DOI： 10.1186/s40623-023-01930-4

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