Storm-enhanced plasma density features investigated during the Bastille Day Superstorm

摘要

Field-aligned passes track true profiles. Such Defense Meteorological Satellite Program passes permitted investigating storm-enhanced plasma density (SED) feature development during the Bastille Day Superstorm in a comprehensive way. We tracked equatorial ionization anomaly (EIA) and SED features and their underlying forward fountain circulation and downward SED plume plasma flows, respectively. Westward subauroral polarization stream E fields detaching plasma and producing SED plumes were also detected. We assessed the effects of South Atlantic Magnetic Anomaly and summer-towinter interhemispheric plasma flows on the EIA and found a southward dipping gradient in drift/flow when no storm/evening-related fountain strengthening occurred. We investigated the relative importance of different plasma sources in SED development. An extremely large plasma enhancement seen over Florida at 2200 UT on 15 July 2000 was a SED feature that was tracked by many GPS total electron content (TEC) maps as a 200 TEC unit ( TECU) enhancement. We tracked its equally large conjugate pair over Trelew (Argentine Patagonia) and unraveled their development. Their underlying SED plume supplied most of the plasma. Appearing between these two SED features, a small and highly asymmetrical EIA offered on each side a low baseline upon which the downward streaming SED plume plasma piled up. Contradicting a currently accepted explanation, there was no enhanced fountain action detected to contribute 150 TECU to the 200 TECU. Later (2400 UT), there was enhanced fountain action, but SED plume contribution still dominated. Proven by observational evidence, SED development is a complex process of SED plume plasma flows and equatorward wind effects that cannot be described by one single explanation.