Successful observation of space disturbances caused by a super geomagnetic storm: suppression of the supply of ionized atmosphere into space

2025-11-21

A research group led by Designated Assistant Professor Dr. Atsuki Shinbori, Dr. Naritoshi Kitamura, Dr. Kazuhiro Yamamoto, Professor Dr. Yoshizumi Miyoshi, and Associate Professor Dr. Yuichi Otsuka, analyzed observation data obtained from the Arase satellite and the Global Navigation Satellite System (GNSS).

Observational data revealed that the plasmasphere, which typically extends into space up to 4 to 6 times the Earth’s radius (6,378 km: equatorial radius), rapidly contracted to an altitude of 1.5 times the Earth’s radius. It took more than four days for the plasmasphere to recover to its quiet-time conditions. Statistical analysis also showed that this recovery time was approximately twice as long as during a typical geomagnetic storm. Furthermore, GNSS ionospheric electron density observations revealed that electron density across a broad region from high to low latitudes decreased by up to 90% compared to quiet-time conditions, and the low-density state in the ionosphere persisted for at least two days.

This study has shown that the abnormal electron density depletion in the ionosphere caused by such super geomagnetic storms suppresses the recovery of the plasmasphere extending into the space above the ionosphere for the first time through observational data analysis. Ionospheric electron density depletion causes HF shortwave communication disruptions that rely on ionospheric reflection. Furthermore, changes in the spatial structure of the plasmasphere during geomagnetic storms control the electromagnetic environment involved in the generation of high-energy particles in geospace. These are elements requiring forecasting from a space weather perspective for the safe utilization of space. The findings of this study represent an important case contributing to predicting space environment variations around Earth during rare super geomagnetic storms.

The research results will be published in Earth, Planets, and Space, an international journal of Earth Sciences, on November 20, 2025.

Reference:
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, Characteristics of temporal and spatial variation of the electron density in the plasmasphere and ionosphere during the May 2024 super geomagnetic storm, Earth Planets Space, 2025. https://doi.org/10.1186/s40623-025-02317-3.

Press release from Nagoya University:
https://en.nagoya-u.ac.jp/news/articles/how-superstorm-gannon-squeezed-earths-plasmasphere-to-one-fifth-its-size/