Comparative Analysis of Optical Observation Characteristics between PMAFs and Throat Aurora

Both Poleward Moving Auroral Forms (PMAFs) and throat aurora are typical transient auroral structures occurred near the magnetic noon. Previous studies have shown that throat auroras contain PMAFs. However, their characteristics and the correlation between these two auroras are not clear yet. By using the observation data of the high-resolution All-Sky Imagers (ASI) at the Yellow River Station in Arctic, together with solar wind and Interplanetary Magnetic Field (IMF) observations, the evolution characteristics of polar ionospheric PMAFs and the throat aurora are detailedly analyzed. It was found that a series of PMAFs and throat auroras appeared in the field of view of the all-sky imagers of the Yellow River Station. Among them, PMAFs mainly occurred in polar side of the equatorial boundary of aurora oval dayside of cusp area, were distributed along the east-west direction, and extended to the high latitude after brightening. Throat auroras were distributed along the north-south direction, which extended to low latitude from equatorward of discrete auroral oval and moved to the west after brightening, usually exist in the side of PMAFs. The frequency of PMAFs during observed period is higher than that of the throat aurora. When PMAFs and the throat aurora appear simultaneously, PMAFs can appear almost simultaneously with throat aurora or slightly later than throat aurora, and have a shorter duration than throat aurora. Based on the above observations, we suggest that magnetopause reconnection corresponding to PMAFs and magnetopause reconnection mapping to throat aurora caused by magnetopause indentations are two relatively independent processes happening in adjacent magnetopause region. The formation processes of the two auroral events are relatively independent, and there may be no mutual triggering relationship.