[PEM13-05] Characteristics of ion upflows from the low-altitude ionosphere observed by EISCAT
Keywords:Ion upflow, Molecular ion, Ionospheric heating, EISCAT radar, Arase (ERG) satellite
Three ion upflow events from the low-altitude ionosphere during geomagnetically disturbed periods (Dst < -30 nT) are analyzed in detail using the EISCAT uhf radar data. These ion upflows have similar features: the upward velocity along the field aligned direction with ion temperature enhancement at 200-400 km altitudes and electron temperature enhancement at 100-120 km altitudes. It indicates that the ion frictional heating caused by strong electric field formed these ion upflows from the low-altitude ionosphere. On the other hand, we found ion upflow events from the low-altitude ionosphere which showed different features from the above three events. Geomagnetic conditions are less active (Dst ~ 0 nT, AE ~ 200 nT) in these latter events. The ion upflows occurred with no significant ion heating but with electron density and temperature enhancement. It suggests that electron heating caused by soft electron precipitation created the second type of the ion upflows from the low-altitude ionosphere.