Optical and SuperDARN radar observations of dusksideshock aurora over Zhongshan Station

Abstract

We present observations of a duskside shock aurora occurred on 21 April 2001 by the SuperDARN radar at SyowaStation and the all-sky camera at Zhongshan Station (ZHS) in Antarctica when the radar was operated in fast-scan mode coveringthe ZHS region. With the two independent data sets, we examine ionospheric plasma convection and aurora arising from a suddenimpulse (SI) event associated with an interplanetary shock. During the transient shock compression, the aurora was quiescentwithout any optical emission at the preliminary impulse of the SI. About 7 min later, a new thin auroral arc with brighter emissionsand a lifetime of ~14 min expanded westward from the region above ZHS during the main impulse of the SI. SuperDARN radarline-of-sight measurements showed periodical oscillation in the flow direction with ultra-low-frequency waves having a period of~8 min during the shock compression. We suggest that downward field-aligned current during the preliminary impulse stage of theSI was the main driver of the first plasma flow reversal, and the subsequent new discrete auroral arc may be associated withfield-aligned acceleration in the region of the main impulse related upward field-aligned currents. The ground magnetometer observationssuggest that the oscillation of the ionospheric convection on the duskside was associated with field line resonance activity.