Solar‐Wind Triggering of Substorm Onset During the May 2024 Superstorm: Coordinated Global Observations and Simulations
Year: 2026
Type: article
Abstract: Substorms are often described by a loading‐unloading cycle, where onset follows gradual accumulation of solar wind magnetic flux in the magnetosphere. Yet observations indicate that intense substorms can also be directly driven, though the underlying mechanism remains unresolved. For the first time, global observations strongly indicate that substorm triggering is linked to enhanced dayside‐driven convection and Region 1 FAC, supported by simulations. At 17:17UT during the May 2024 superstorm, a shock‐compressed southward interplanetary magnetic field enhanced sunward convection and auroral currents. These rapidly extended to the nightside, initiating substorm expansion within 6 min. Simulations reproduce this response, revealing that dayside‐driven convection of closed field lines depleted nightside flux and thinned the current sheet. This lowered onset threshold and triggered substorm expansion with negligible flux loading. Following onset, nightside flux loading became significant as a reconnection X‐line formed near 10 Earth radii, extended azimuthally, and supported a global substorm current wedge.
Source: Geophysical Research Letters
DOI: 10.1029/2025gl119629
Institutions: Chinese Academy of Sciences, National Space Science Center, State Key Laboratory of Space Weather, Instituto Nacional de Pesquisas Espaciais, Peking University, European Space Agency, European Space Research and Technology Centre, Macau University of Science and Technology, State Key Laboratory of Lunar and Planetary Sciences
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
SDG: Climate action
Open Access status: gold
Estimated APC paid: $3,190
OpenAlex ID: W7128910412