Polar Ion Temperature Variations During the 22 January 2012 Magnetic Storm

Abstract

AbstractWe study the 22 January 2012 magnetic storm, during which some localized neutral density (DN) increases developed, and its polar ion temperature (Ti) variations in terms of the earthward Poynting flux (S||) deposited into the coupled ionosphere‐thermosphere system. We investigate the storm's nature, some flow channel events that are the ionospheric signatures of flux transfer events triggered by magnetic reconnections, and the resultant thermospheric responses. We utilize solar and interplanetary magnetic field data and multi‐instrument topside ionospheric and thermospheric measurements. Results reveal the presence of antisunward propagating solar wind Alfven waves during the various storm phases triggering flux transfer events/flow channel events and launching atmospheric gravity waves whose Ti signatures appeared as episodic Ti variations. Various scenarios demonstrate the direct correlation between S|| and DN and the irregular Ti responses within/above flow channels that we explain in terms of frictional heating (Tfrc). We identify Ti responses during various flow channel events as (1) direct/intermittent and (2) opposite, with S|| and DN reflecting the respective underlying flow channel development at the time of detection as (1) early stage when Tfrc was high due to the still large velocity differences between ions and neutrals and as (2) late stage when Tfrc ceased since ions and neutrals moved together. Ti oscillations are observed to be originating from polar or auroral flow channels and propagating across the polar cap toward the equator. We conclude that antisunward solar wind Alfven waves had a significant impact on Ti variability during this storm by modulating magnetic reconnection and launching atmospheric gravity waves.