Multi-process driven unusually large equatorial perturbation electric fields during the April 2023 geomagnetic storm

Abstract

The low latitude ionosphere and thermosphere are strongly disturbed during and shortly after geomagnetic storms. We use novel Jicamarca radar measurements, ACE satellite solar wind, and SuperMAG geomagnetic field observations to study the electrodynamic response of the equatorial ionosphere to the 23, 24 April 2023 geomagnetic storm. We also compare our data with results from previous experimental and modeling studies of equatorial storm-time electrodynamics. We show, for the first time, unusually large equatorial vertical and zonal plasma drift (zonal and meridional electric field) perturbations driven simultaneously by multi storm-time electric field mechanisms during both the storm main and recovery phases. These include daytime undershielding and overshielding prompt penetration electric fields driven by solar wind electric fields and dynamic pressure changes, substorms, as well as disturbance dynamo electric fields, which are not well reproduced by current empirical models. Our nighttime measurements, over an extended period of large and slowly decreasing southward IMF Bz, show very large, substorm-driven, vertical and zonal drift fluctuations superposed on large undershield driven upward and westward drifts up to about 01 LT, and the occurrence of equatorial spread F irregularities with very strong spatial and temporal structuring. These nighttime observations cannot be explained by present models of equatorial storm-time electrodynamics.

Responses of Field‐Aligned Currents and Equatorial Electrojet to Sudden Decrease of Solar Wind Dynamic Pressure During the March 2023 Geomagnetic Storm

“…Many studies have used EEJ variations to probe the presence of PPEFs that are attributed to interplanetary magnetic field (IMF) variations (e.g., Yizengaw et al, 2011Yizengaw et al, , 2016 or solar wind dynamic pressure pulses (e.g., Nilam et al, 2020Nilam et al, , 2023. Understanding the sources and the process of PPEFs continues to be a subject of ongoing investigation (Fejer et al, 2024;Kelley et al, 2003). This paper reports the observations of the M-I coupling and its effect on the equatorial ionosphere in response to a sudden decrease of the solar wind dynamic pressure during the main phase of the 23 March 2023 geomagnetic storm.…”

Impacts of Storm Electric Fields and Traveling Atmospheric Disturbances Over the Americas During 23–24 April 2023 Geomagnetic Storm: Experimental Analysis

“…The superposition of Traveling Atmospheric Disturbances (TADs), Disturbance Dynamo (DD), and prompt penetration electric fields (PPEFs) by undershielding or overshielding events over those of quiet time conditions frequently occurs during large geomagnetic storms. Recently, Fejer et al (2024) published historical reports of the ionospheric electric field impacts from geomagnetic disturbances. In addition, they also discussed, in a clear and innovative way, the anomalous variations of the equatorial electric field during the 23 and 24 April 2023.…”

“…Important players are thermospheric neutral winds and the electric fields of ionospheric dynamos (Kelley, 2009). The complexity of the competition increases, due to the increase in the number of players, for periods of geomagnetic disturbances and this has been studied for several decades, as pointed out by Fejer et al (2024). The superposition of Traveling Atmospheric Disturbances (TADs), Disturbance Dynamo (DD), and prompt penetration electric fields (PPEFs) by undershielding or overshielding events over those of quiet time conditions frequently occurs during large geomagnetic storms.…”

“…This increase lasts 2 hr, reaching a maximum of 81 m/s at 19:37 UT. A detailed description of this storm electric field morphology was recently published byFejer et al (2024). All Group 1 hmF2 values increase following the E × B drift variations, including…”

Solar wind-magnetosphere-ionosphere coupling and its impact on equatorial ionospheric electrodynamics during the 23 March 2023 geomagnetic storm: Effect of sudden decrease of solar wind dynamic pressure

“…Understanding the sources and the process of PPEFs continues to be a subject of ongoing investigation (Kelly et al, 2003;Fejer et al, 2024). This paper reports the observations of the M-I coupling and its effect on the equatorial ionosphere in response to a sudden decrease of the solar wind dynamic pressure during the main phase of the 23 March 2023 geomagnetic storm.…”