Multi-Instrument Observations of the Evolution of Polar Cap Patches Associated With Flow Shears and Particle Precipitation
Zhang, Duan; Zhang, Qing-He; Oksavik, Kjellmar; Xing, Zan-Yang; Lyons, L.R.; Yang, Hui-Gen; Li, Guo-Jun; Hosokawa, Keisuke; Shinbori, Atsuki; Ma, Yu-Zhang; Wang, Yong; Wang, Xiang-Yu
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Journal of Geophysical Research (JGR): Space Physics. 2023, 128 (12), e2023JA032176. 10.1029/2023JA032176Sammendrag
Simultaneous observations from Defense Meteorological Satellite Program, Swarm, Resolute Bay all-sky imagers, GPS Total Electron Content and Super Dual Auroral Radar Network, are used to investigate the evolution and key characteristics of the Tongue of Ionization (TOI) being restructured into a polar cap patch. Six satellites crossed the TOI of patch as it moved from the dayside to the nightside. It was initially hot, then a mix of both cold and hot, and finally it became a cold patch. This suggests that cold patch is not only a result of solar extreme ultraviolet radiation, but may also develop when a hot patch cools down. Soft-electron precipitation and flow shears both contribute to the TOI restructuring and the appearance of polar cap patch. The plasma density of patch at ∼500 km was at least 4 times higher than at ∼800 km. The plasma density enhancement gradually decreased as the patch evolved due to decreased production and transport of cold nightside low-density plasma. Moreover, the duskward motion of the patch was influenced by changes in the ionospheric convection pattern.