Simultaneous optical and radar observations of poleward moving auroral forms under different IMF conditions

Abstract

Using high temporal resolution optical data obtained from three-wavelength all-sky imagers at Chinese Yellow RiverStation in the Arctic, together with the EISCAT Svalbard radar (ESR) and SuperDARN radars, we investigated the dayside polewardmoving auroral forms (PMAFs) and the associated plasma features in the polar ionosphere under different interplanetarymagnetic field (IMF) conditions, between 0900 and 1010 UT on 22 December 2003. Simultaneous optical and ESR observationsrevealed that all PMAFs were clearly associated with pulsed particle precipitations. During northward IMF, particles can precipitateinto lower altitudes and reach the ionospheric E-region, and there is a reverse convection cell associated with these PMAFs.This cell is one of the typical signatures of the dayside high-latitude (lobe) reconnection in the polar ionosphere. These resultsindicate that the PMAFs were associated with the high-latitude reconnection. During southward IMF, the PMAFs show larger latitudinalmotion, indicating a longer mean lifetime, and the associated ionospheric features indicate that the PMAFs were generatedby the dayside low-latitude reconnection.