11:15 AM - 11:30 AM
[PEM15-09] Properties of ion upflows in the low-altitude polar ionosphere during CIR- and CME- driven magnetic storms based on the long-term EISCAT observations
Keywords:ion upflow, corotating interaction region (CIR), coronal mass ejection (CME), magnetic storms, polar ionosphere, EISCAT radars
We used data from the EISCAT ultra high frequency (UHF) radar at Tromsø (Invariant Latitude: 66°12' N) and Svalbard 42m antenna radar (ESR) at Svalbard (Invariant Latitude: 75°10' N) during CIR- and CME-driven magnetic storms from 1996 to 2015. We used 5-minute time resolution data when the radar was looking along the magnetic field line. The ionospheric parameters such as electron density, ion velocity, and ion and electron temperatures were averaged between 250 and 350 km and we screened data to exclude unrealistic values. The results show that ion upflows in the low-altitude ionosphere were mainly detected in the dayside and nightside at Tromsø during both CIR- and CME- driven magnetic storms. On the other hand, the upward flux at Svalbard was not enhanced in nightside but remarkable in dawnside after CIR-driven storms, whereas it increased from the low-altitude region in the nightside only after CME-driven large storms. The ion upflows were detected in the duskside at Tromsø only during CME-driven large storms. We also estimated the generation mechanisms of upflows by comparing ion and electron temperatures between pre-storm time and after storm onset. The frictional heating mainly caused upflows during CME-driven storms at both locations and possibly in the dawnside during CIR-driven storms at Svalbard, whereas the precipitation mainly caused upflows during CIR-driven storms at both locations and possibly in the nightside during CME-driven small storms at Tromsø.
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