12:00 PM - 12:15 PM
[PEM10-11] Effects of CIR- and CME-driven magnetic storms on ion upflows in the low-altitude polar ionosphere
Keywords:ion upflow, corotating interaction region (CIR), coronal mass ejection (CME), magnetic storms, polar ionosphere, EISCAT radars
We used data from the EISCAT UHF radar at Tromsø (69º35'N, 19º14'E, Invariant Latitude: 66º12'N) and Svalbard radar at Longyearbyen (78º09'N, 16º03'E, Invariant Latitude: 75º10'N) from January 1996 to January 2016, and investigated statistical properties of ion upflows and ionospheric conditions during CIR- and CME-driven magnetic storms. We used 5-minute time resolution data when the radar was looking along the local magnetic field line. The ionospheric parameters such as electron density, ion velocity, and ion and electron temperatures were averaged over 250-350 km altitudes. We screened data to exclude unrealistic values with the following criteria: Absolute value of ion velocity was less than 1500 m/s, ion and electron temperatures were less than 10000 K, and electron density was more than 1010m-3and less than 1013m-3. We also selected reliable data based on the error values of ion and electron temperatures: The error value was less than 50% of each temperature. To understand the similarity and difference between low- and high- altitude upflows, we compared obtained results with those from the previous study [Ogawa et al., 2019]. The results show that low-altitude ion upflows were observed mainly in nightside and dawnside at Tromsø and Svalbard during magnetic storms. We also investigated the dependence of the low-altitude upflows on ion and electron temperatures to discuss the generation mechanisms. We assumed contribution from the frictional heating with ion temperature increase by >15% and the ratio of enhancement on electron temperature at ~110km, which indicates the enhancement of the electric field, were more than 1% compared to pre-storm value. On one hand, contribution of electron precipitations is assessed with electron temperature increase by >15%. The results indicate that the frictional heating mainly caused upflows during CME storms at both locations and possibly in dawnside during CIR storms at Svalbard, whereas precipitations mainly caused upflowsduring CIR storms at both locations and possibly in duskside during large CME storms at Tromsø.