Magnetosphere‐Ionosphere‐Thermosphere (M‐I‐T) Coupling Leading to Equatorial Upward and Westward Drifting Supersonic Plasma Bubble Development and Amplified Subauroral Polarization Streams (SAPS) During the January 21, 2005 Moderate Storm

Abstract

AbstractBy utilizing multipoint observations, we investigate the January 21, 2005 moderate storm's prompt penetration electric field (PPEF) effects in the American sector, Rayleigh‐Taylor (R‐T) instability driven polarization electric (E) field effects in the African sector, and disturbance dynamo electric field (DDEF) effects in the Northern Hemisphere. We study how these E field effects impacted the equatorial ionization anomaly (EIA) and underlying forward fountain, the midlatitude trough, and the subauroral polarization streams (SAPS). In the daytime sector during the initial phase, the PPEF development was produced by solar wind pressure enhancements. In the dusk sector, the undershielding PEFs triggered R‐T instability mechanisms, which impacted the EIA during a prereversal enhancement (PRE) like scenario and afterwards. These led to the development of supersonic plasma bubbles drifting upward and westward. Supersonic bubbles are characteristics of superstorms, and their detections further verify the January 21, 2005 moderate storm's turbulent and superstorm nature. While the disturbance dynamo‐driven anti‐Sq current system operated, the net subauroral westward currents became enhanced and the net zonal (E‐ and F‐region) drift created a deep O+ trough that deepened the midlatitude trough and led to amplified SAPS flows via positive feedback mechanisms. We conclude that strong magnetosphere‐ionosphere‐thermosphere coupling was present at equatorial latitudes where forward fountain plasma drift‐signatures were seen in the thermospheric neutral wind speed data and where the supersonic bubbles developed, and at subauroral latitudes where the midlatitude trough became deepened during the anti‐Sq current system's operation amplifying the SAPS flows by positive feedback mechanisms.