Faculty Profiles - SHINBORI Atsuki

Papers - SHINBORI Atsuki

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Thousand-Kilometer-Scale Wavelike Undulations in Ionospheric Plasma Bubble Lifetime and Development Over Wide Longitudes Reviewed Open Access

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

GEOPHYSICAL RESEARCH LETTERS Vol. 53 ( 6 ) 2026.3

Source altitudes and heating properties of electron conics observed at high altitudes by the Arase satellite Reviewed International coauthorship Open Access

Hiroki Ishimaru, Shun Imajo, Yoshizumi Miyoshi, Yoichi Kazama, Kazushi Asamura, Ayako Matsuoka, Yoshiya Kasahara, Shiang-Yu Wang, Sunny W. Y. Tam, Chae-Woo Jun, Mariko Teramoto, Kazuhiro Yamamoto, Fuminori Tsuchiya, Atsushi Kumamoto, Atsuki Shinbori, Tomoaki Hori, Iku Shinohara, Tzu-Fang Chang, Bo-Jhou Wang

Earth, Planets and Space 2026.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

Electron conics are a distinct type of electron distribution observed in Earth’s magnetosphere, characterized by enhanced fluxes of upgoing electrons at several-keV energies, particularly in the auroral acceleration region. This study analyzes high-altitude (27,000–32,000 km) observations made by the Arase satellite to investigate the characteristics of electron conics after passing through the heating region, employing the high angular resolution of the low-energy particle experiments—electron analyzer (LEPe) onboard the satellite. We analyzed eight electron conic events between 2017 and 2022 to estimate their source altitudes using mirror ratios and potential differences and by comparing pre- and post-heating data to investigate heating properties. Our results show that the source region of conics has an upper boundary at 9,000–14,000 km, with the peak flux originating from a central altitude of 3,000–7,000 km. This region spatially coincides with the source of auroral kilometric radiation (AKR): the central altitude of the source of conics corresponds to the lower boundary of the AKR source, suggesting that a longer residence time of particles within the AKR source region leads to stronger heating. The comparison of pre- and post-heating populations demonstrated that upgoing conic electrons exhibit higher temperatures and lower densities. The number flux remains conserved, indicating the energization of a magnetospheric population, whereas the energy flux is enhanced by up to a factor of four, significantly higher than that reported in previous studies. A test particle simulation, using observed plasma parameters and incorporating stochastic perpendicular heating, reproduces the main features of observed conics in terms of both energy and pitch angle. Our simulation shows that electron conics evolve into narrow, field-aligned beams at higher altitudes, suggesting that some of the anti-Earthward-flowing beams observed in the magnetotail may actually be unresolved conics. These findings contribute to the understanding of energy transport between the auroral acceleration region and the magnetotail and show the importance of high-angular-resolution instrumentation.

Graphical Abstract

DOI： 10.1186/s40623-026-02399-7

Open Access

researchmap

The Dominant Role of the Electron Isotropy Boundary in Controlling Earth's Outer Radiation Belt Electron Lifetimes Reviewed Open Access

Man Hua, Xiaofei Shi, Jacob Bortnik, Anton Artemyev, Vassilis Angelopoulos, Yoshizumi Miyoshi, Takefumi Mitani, James L. Burch, Takeshi Takashima, Tomoaki Hori, Ayako Matsuoka, Mariko Teramoto, Kazuhiro Yamamoto, Yoshiya Kasahara, Fuminori Tsuchiya, Atsushi Kumamoto, Atsuki Shinbori, Iku Shinohara

GEOPHYSICAL RESEARCH LETTERS Vol. 53 ( 3 ) 2026.2

Power attenuation of Pc1 waves during propagation from the magnetosphere to the ionosphere observed by the Arase satellite and PWING ground stations Reviewed Open Access

Jaeyoung Kwak, Chae-Woo Jun, Yukinaga Miyashita, Jaeheung Park, Yoshizumi Miyoshi, Kazuo Shiokawa, Ayako Matsuoka, Mariko Teramoto, Kazuhiro Yamamoto, Iku Shinohara, Yoshiya Kasahara, Fuminori Tsuchiya, Atsushi Kumamoto, Atsuki Shinbori, Dmitry Baishev, Igor Poddelsky

Earth, Planets and Space 2026.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

Understanding how the properties of Pc1 waves change during their propagation from the magnetospheric source regions to the middle or low-latitude ionosphere have not yet been clearly revealed by observations. In this study, we present the first quantitative comparison of Pc1 wave power attenuation both along the geomagnetic field lines and in the ionospheric wave ducts, using simultaneous observations from the Arase satellite and dynamical variation of Particles and Waves in the INner magnetosphere using Ground-based network observations (PWING) ground magnetometers. One of our key findings is that the polarization sense of the waves changed from left-handed polarization (LHP) at the satellite to right-handed polarization (RHP) on the ground, providing observational evidence of polarization transformation from space to the ionosphere. By examining polarization angles, we confirm that the Pc1 waves observed at multiple ground stations originated from the same magnetospheric source as the EMIC waves detected by the Arase. Importantly, we quantify the wave power attenuation factor along the magnetic field line to be only 0.37 dB/1000 km, which is nearly an order of magnitude smaller than that in the ionospheric wave duct (4.7–8.2 dB/1000 km). This result establishes a previously unreported minimum Pc1 wave attenuation rate in the magnetosphere, highlighting that the wave energy loss occurs more rapidly in the ionospheric duct than in space. These findings provide new insights into Pc1 wave transmission mechanisms and emphasize the importance of combined space- and ground-based observations for characterizing wave propagation processes across geospace.

Graphical Abstract

DOI： 10.1186/s40623-026-02372-4

Open Access

researchmap

The possibility of using all-sky meteor radar to study the spatial features of ionospheric plasma bubbles Reviewed

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

SCIENCE CHINA-TECHNOLOGICAL SCIENCES Vol. 69 ( 1 ) 2026.1

Comparison of repetition period of whistler-mode chorus and relativistic electron precipitation based on conjunction events of Arase and CALET Reviewed Open Access

Arai M., Katoh Y., Kataoka R., Torii S., Akaike Y., Teramoto M., Kumamoto A., Tsuchiya F., Kasaba Y., Miyoshi Y., Kasahara Y., Matsuda S., Shinohara I., Yamamoto K., Matsuoka A., Hori T., Shinbori A.

Proceedings of Science Vol. 501 2025.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of Science

The dynamic evolution of Earth’s radiation belts is an important topic of space weather research to mitigate the possible malfunctions of satellites orbiting, especially at GEO. Relativistic electron precipitation (REP) detected at LEO indicates when, where, and how the loss process of radiation belt electrons takes place. REP is detected as the enhancement of downward electron counts in the MeV energy range. Pitch angle scattering by whistler-mode chorus emissions in the magnetosphere is a plausible mechanism responsible for REP. Previous studies revealed that the repetition periods of REP and chorus are statistically similar, but those in the simultaneous observation of REP and chorus have not been analyzed yet. In this study, we investigated the repetition periods of both REP and chorus based on the conjunction events of the ISS/CALET at LEO and the Arase satellite in the magnetosphere. We defined REP by using the count rates observed with CALET’s CHarge Detector (CHD) as the ratio of CHD-X (upper layer) to CHD-Y (lower layer) count rates ≥1.2. The threshold energies to detect the precipitating electrons are 1.6 MeV and 3.6 MeV for CHD-X and CHD-Y, respectively. Chorus appears in the spectra with a hierarchical time scale consisting of several hundred milliseconds, corresponding to the repetition of each chorus element, and a few seconds, corresponding to a group of chorus elements. The same hierarchical time scale can be expected for REP. We used CHD count-rate data with a 1-second time cadence to investigate the fluctuations of REP in seconds. Additionally, we used higher time-resolution count-rate data with a time resolution of up to 20 Hz to investigate the fluctuations of REP in hundred milliseconds. Similarly, we analyzed the repetition periods of chorus emissions using Arase satellite data. We use Arase/WFC data, which measures 64 kHz sampled waveforms over limited time intervals, to analyze the fine-scale structure of individual chorus elements and compare them with the repetition period of REP on a millisecond time scale. The present study reveals that the repetition periods of REP occurred in a time scale corresponding to the chorus elements observed in the magnetosphere.

DOI： 10.22323/1.501.1385

Open Access

Scopus

Bridging the Gap Between the Earth's Ionosphere and Plasmasphere Reviewed Open Access

Artem Smirnov, Yuri Shprits, Hermann Luhr, Elena A. Kronberg, Jerry Goldstein, Yoshizumi Miyoshi, Fabricio Prol, Alessio Pignalberi, Natalia Buzulukova, Nicholas Pedatella, Bernhard Haas, Dedong Wang, Yoshiya Kasahara, Fuminori Tsuchiya, Shoya Matsuda, Atsuki Shinbori, Ayako Matsuoka

GEOPHYSICAL RESEARCH LETTERS Vol. 52 ( 23 ) 2025.12

Radio emissions reveal Alfvénic activity and electron acceleration prior to substorm onset. Reviewed Open Access

Wu SY, Whiter DK, Lamy L, Wang MM, Zarka P, Jackman CM, Ye SY, Waters JE, Fogg AR, Mende SB, Kaweeyanun N, Kasaba Y, Kurita S, Kojima H, Paxton LJ, Kasahara Y, Miyoshi Y, Shinbori A, Tsuchiya F

Nature communications Vol. 16 ( 1 ) page： 10553 2025.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Nature Communications

Magnetospheric substorms are among the most dynamic phenomena in the Earth’s magnetosphere, yet their triggering mechanisms remain unclear. Ground-based observations have identified wave-like aurora as precursors to substorms. Here, we report a new precursor feature in space-based observations of auroral kilometric radiation (AKR), marked by the appearance of emissions with slowly frequency-drifting tones (<2 kHz/s) above 100 kHz. Simultaneous multi-instrument observations and statistical analysis suggest that these AKR precursors occur concurrently with wave-like aurora, either manifesting as pseudo-breakup features (with about 5 min duration) or as pre-onset activity (about 2 min prior to substorm expansion), indicating a common driving mechanism. Analysis of the emissions with frequency-drifting tones suggests that they are linked to moving double layers driven by dispersive Alfvén waves, consistent with an Alfvénic acceleration mechanism for pre-onset aurora. These findings highlight the importance of Alfvénic activity in substorms and suggest that Alfvénic acceleration is not only responsible for optical auroral features but also for radio emissions, potentially explaining also the ubiquitous frequency-drifting emission features observed at other magnetized planets like Saturn and Jupiter.

DOI： 10.1038/s41467-025-65580-8

Open Access

Scopus

PubMed

Characteristics of temporal and spatial variation of the electron density in the plasmasphere and ionosphere during the May 2024 super geomagnetic storm Reviewed Open Access

Atsuki Shinbori, Naritoshi Kitamura, Kazuhiro Yamamoto, Atsushi Kumamoto, Fuminori Tsuchiya, Shoya Matsuda, Yoshiya Kasahara, Mariko Teramoto, Ayako Matsuoka, Takuya Sori, Yuichi Otsuka, Michi Nishioka, Septi Perwitasari, Yoshizumi Miyoshi, Iku Shinohara

EARTH PLANETS AND SPACE Vol. 77 ( 1 ) 2025.11

Unusual Phase Alignment of Nighttime Electrified Medium-Scale Traveling Ionospheric Disturbance After Moderate Geomagnetic Storms and Response to Substorms Reviewed Open Access

Dipjyoti Patgiri, Yuichi Otsuka, P. R. Shreedevi, Geetashree Kakoti, Alok Kumar Ranjan, Rahul Rathi, Atsuki Shinbori, Michi Nishioka, Septi Perwitasari

GEOPHYSICAL RESEARCH LETTERS Vol. 52 ( 20 ) 2025.10

Superstorm-driven electron temperature (<i>T</i><sub>e</sub>) anomalies in the topside low-latitude ionosphere: role of the equatorial ionization anomaly (EIA) Reviewed Open Access

P. R. Shreedevi, Achuthan S. Nair, Yoshizumi Miyoshi, Stephan C. Buchert, Yuichi Otsuka, Atsuki Shinbori, Lalitha G. Krishnan, Septi Perwitasari, Michi Nishioka

EARTH PLANETS AND SPACE Vol. 77 ( 1 ) 2025.10

Eastward transients in the dayside ionosphere. I. Electrodynamics on closed field lines Reviewed International journal Open Access

Magnus F. Ivarsen, Jean-Pierre St-Maurice, Glenn C. Hussey, Daniel Billet, Devin R. Huyghebaert, Yaqi Jin, Yukinaga Miyashita, Satoshi Kasahara, Kaili Song, P. T. Jayachandran, Shoichiro Yokota, Yoshizumi Miyoshi, Kazuhiro Yamamoto, Atsuki Shinbori, Yoshiya Kasahara, Iku Shinohara, Ayako Matsuoka

PHYSICAL REVIEW E Vol. 112 ( 4 ) page： 045204 - 045204 2025.10

Multiple-Event Study of Substorm Electric Field Penetration Into Middle Latitudes Based on Simultaneous Observation of 630-nm Airglow Enhancements at Three Stations Reviewed Open Access

Morita, S; Shiokawa, K; Otsuka, Y; Nshitani, N; Shinbori, A; Fujimoto, A; Yoshikawa, A; Nishioka, M; Perwitasari, S; Yamamoto, M; Sori, T

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 130 ( 10 ) 2025.10

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

It is known that convection electric fields develop in the polar region associated with substorm onset, and a westward electric field penetrates to lower latitudes on the night side. Two-dimensional observations of 630-nm airglow enhancements associated with the westward electric field can be conducted using all-sky cameras at middle latitudes. We investigated seven simultaneous 630-nm airglow enhancement events using all-sky cameras at Rikubetsu (43.5°N, 143.8°E), Shigaraki (34.9°N, 136.1°E), and Sata (31.0°N, 130.7°E) in Japan. A multi-event multi-point study of 630-nm airglow enhancement has been conducted for the first time. These seven events were found from 1,800 nights in 11 years, from 2002 to 2012, indicating that simultaneous 630-nm airglow enhancements over Japan were very rare. Five of these events occurred during storms, suggesting that simultaneous enhancement requires a large penetrating electric field associated with storm-time substorms. In three events, the enhancement was identified as occurring simultaneously with clear substorm onsets, while the other four events were also associated with high-latitude magnetic disturbances. In all seven events, we observed downward motion of the ionosphere associated with the airglow enhancement. These results indicate that they are due to the westward electric field in the substorm undershielding state. In two events, the time at the end of the 630-nm airglow enhancement correlated well with the increase in ionospheric altitude observed by ionosondes and an FM-CW radar. This increase in ionospheric altitude and termination of the airglow enhancement could be caused by eastward electric field penetration associated with overshielding in the magnetosphere.

DOI： 10.1029/2025JA033721

Open Access

Web of Science

Scopus

Distinct Global Distribution of Electrostatic Electron Cyclotron Harmonic Waves in Earth's Magnetosphere Revealed by Multi-Satellite Observations Reviewed Open Access

Yuequn Lou, Binbin Ni, Xing Cao, Qianli Ma, Yoshizumi Miyoshi, Dedong Wang, Shuqin Chen, Jiaming Li, Xudong Gu, Xin Ma, Qi Zhu, Yoshiya Kasahara, Shoya Matsuda, Atsuki Shinbori, Ayako Matsuoka, Mariko Teramoto, Kazuhiro Yamamoto, Iku Shinohara

GEOPHYSICAL RESEARCH LETTERS Vol. 52 ( 17 ) 2025.9

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

Joe Hughes, Ian Collett, Camella Nasr, Anastasia Newheart, Ryan Kelly, Scott Thaller, Raj Patel, Connor Johnstone, Elijah Vance, Houjun Wang, Nathan Re, Ben Tatman, Yoshiya Kasahara, Fuminori Tsuchiya, Tomoaki Hori, Shoya Matsuda, Atsushi Kumamoto, Mariko Teramoto, Atsuki Shinbori, Ayako Matsuoka, Kazuhiro Yamamoto, Yoshizumi Miyoshi, Iku Shinohara

ADVANCES IN SPACE RESEARCH Vol. 76 ( 5 ) page： 2850 - 2861 2025.9

Reduction of High Latitude Ionospheric Electron Density by the Impact of Negative Solar Wind Pressure Pulse During the Geomagnetic Storm of 23 March 2023 Reviewed Open Access

Geetashree Kakoti, Mala S. Bagiya, Geeta Vichare, Kazuo Shiokawa, P. R. Shreedevi, Nozomu Nishitani, Yuichi Otsuka, Atsuki Shinbori, Michi Nishioka, Septi Perwitasari

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 130 ( 8 ) 2025.8

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

Rui Chen, Yoshizumi Miyoshi, Hong Zhao, Huayue Chen, Xueyi Wang, Yoshiya Kasahara, Shoya Matsuda, Tomoaki Hori, Fuminori Tsuchiya, Atsushi Kumamoto, Atsuki Shinbori, Satoshi Kasahara, Shoichiro Yokota, Kunihiro Keika, Takefumi Mitani, Takeshi Takashima, Ayako Matsuoka, Mariko Teramoto, Kazuhiro Yamamoto, Iku Shinohara

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

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

Shintaro Yoshiura, Yuichi Otsuka, Cathryn M. Trott, Dev Null, Nozomu Nishitani, Keitaro Takahashi, Michi Nishioka, Septi Perwitasari, Atsuki Shinbori

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

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

Weizheng Fu, Yuichi Otsuka, Nicholas Ssessanga, Atsuki Shinbori, Takuya Sori, Michi Nishioka, Septi Perwitasari

EARTH PLANETS AND SPACE Vol. 77 ( 1 ) 2025.5

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Papers - SHINBORI Atsuki