[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-P06] Mid-latitude ionospheric plasma flow observed by SuperDARN Hokkaido East Radar during the storm recovery phase using AMPERE and TIEGCM

*大森 康平¹、西谷 望¹、堀 智昭¹、Lu Gang²、Anderson Brian³、Sarah Sarah³ (1.名古屋大学宇宙地球環境研究所、2.National Center for Atmospheric Research、3.The Johns Hopkins University Applied Physics Laboratory)

キーワード：電離圏、SuperDARN、磁気嵐、AMPERE、TIEGCM

After the onset of a geomagnetic storm, plasma drift can occur in the mid-latitude ionosphere due to various factors such as auroral oval expansion, SAPS, intruding electric fields, overshielding electric fields, and disturbance dynamo, and identifying these physical processes is important for understanding magnetosphere-ionosphere-thermosphere interactions. In order to distinguish between these effects, we studied the origin of westward ionospheric plasma flows observed by the SuperDARN Hokkaido East Radar during the recovery phase of a geomagnetic storm, comparing them with the AMPERE observations of field-aligned currents and TIEGCM simulations of ionospheric plasma flows and neutral winds. The plasma flow velocity was about 100 m/s to 200 m/s in the westward direction and was observed continuously on the night side for about 9 hours. A comparison of the HOK and AMPERE observations indicates that the increase in plasma-flow velocities with a time span of a few tens of minutes corresponds to an increase in upward field-aligned currents. These velocity increases also coincided with substorm onset, indicating that they were due to the effects of the penetration or overshielding electric field associated with the substorm. A comparison of the HOK observations with the results of ion drift simulations by TIEGCM did not confirm the impact of neutral wind-ionospheric plasma collisions. Along with this, other effects need to be considered, such as enhanced high-latitude convection, SAPS effects, and the effects of neutral winds in the overall system. These possible driving mechanisms of mid-latitude ionospheric plasma flow will be discussed in more detail.