Investigating Magnetosphere-Ionosphere-Thermosphere (M-I-T) Coupling Occurring During the 7-8 November 2004 Superstorm

In this study, we investigate the shock-sheath driven 7-8 November 2004 superstorm for its flux transfer events and resultant flow channel (FC) events and associated neutral (D-N) and electron (Ne) density features in order to understand better the underlying coupled magnetosphere (M) and ionosphere (I) processes and responses in the thermosphere (T). We focus on the (i) subauroral, auroral, and polar cap regions, (ii) localized DN increases and associated Ne features and FCs developed, and (iii) energy deposition occurred. Results show the development of localized DN increases (1) within/over FCs and associated enhanced small-scale field aligned currents suggesting Joule heating driving upwelling during forward and reverse polar convections, (2) appearing with Ne increases during storm-enhanced density (SED) events suggesting strong M-I-T coupling and with Ne depletions during plasmaspheric erosion events suggesting weak M-I-T coupling, and (3) in the thermosphere's increasing NO and continuously low O/N-2 composition regions. During erosion events, strong storm-time subauroral polarization streams (SAPS) E fields developed. Meanwhile the well-developed plasmapause appeared with decreased total electron content (TEC) on its poleward side and with increased TEC and Ne (appearing as a shoulder feature that is the signature of SED) on its equatorward side. From these we conclude that although strong M-I-T coupling was apparent during SED events, M-I-T coupling was also strong during erosion events when the combination of strong convection E field and large storm-time SAPS E fields eroded the high-latitude region and thus decreased the high-latitude Ne and TEC.