Exploring Magnetosphere-Ionosphere Responses to Negative Solar Wind Pressure Pulses: Case Study of 23 March 2024

The interaction between the solar wind and Earth’s magnetosphere can induce significant changes in the magnetosphere-ionosphere (M-I) system. This study explores the M-I responses to a negative solar wind pressure pulse event on 23 March 2024. The event was marked by a sharp solar wind dynamic pressure drop of ~10 nPa, which preceded the onset of G2 and G4-class geomagnetic storms on 23 and 24 March 2024. The negative pressure pulse occurred at 14:06 UT, as confirmed by THEMIS satellite observations.

Using Global Navigation Satellite System (GNSS)-Total Electron Content (TEC), ground magnetometer data, and AMPERE observations, the study examined the impacts of the pressure pulse on the coupled M-I system. Observations revealed a pronounced reduction in TEC at high latitudes, particularly in the European afternoon sector, following the pressure drop. This significant perturbation in electron density is postulated to result from the magnetospheric expansion during the negative pressure pulse. The H-component of Earth’s magnetic field exhibited a marked global decrease across all longitude sectors following the pressure drop, attributed to ground perturbations caused by reduced magnetopause currents and weakened magnetospheric fields. AMPERE observations further revealed a reduction in field-aligned current density, corroborating the observed ionospheric and geomagnetic responses.

This study delineates the pressure drop-induced effects from storm-related electrodynamic and neutral dynamic variations by isolating the distinct timing of the pressure pulse event, characterized by steady IMF conditions prior to the onset of the geomagnetic storm. The findings underscore the critical role of negative solar wind pressure pulses as standalone drivers capable of triggering rapid and widespread changes in the M-I system.