Research Article

Unexpected space weather causing the reentry of 38 Starlink satellites in February 2022

¹ National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
² The Graduate University for Advanced Studies, SOKENDAI, Tachikawa, Tokyo 190-8518, Japan
³ Okinawa Institute of Science and Technology, Tancha, Okinawa 904-0495, Japan
⁴ National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
⁵ Faculty of Science and Technology, Seikei University, Musashino, Tokyo 180-8633, Japan
⁶ Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan

^* Corresponding author: kataoka.ryuho@nipr.ac.jp

Received: 23 March 2022
Accepted: 5 October 2022

Abstract

The accidental reentry of 38 Starlink satellites occurred in early February 2022, associated with the occurrence of moderate magnetic storms. A poorly understood structure of Coronal Mass Ejections (CMEs) caused the magnetic storms at unexpected timing. Therefore, a better understanding of minor CME structures is necessary for the modern space weather forecast. During this event, the “up to 50%” enhancement of air drag force was observed at ~200 km altitude, preventing the satellites’ safety operations. Although the mass density enhancement predicted by the NRLMSIS2.0 empirical model is less than 25% under the present moderate magnetic storms, the real-time GAIA simulation showed a mass density enhancement of up to 50%. Further, the real-time GAIA simulation suggests that the actual thermospheric disturbances at 200 km altitude may occur with larger amplitude in a broader area than previously thought.