Dayside auroral emissions controlled by IMF: A survey for dayside auroral excitation at 557.7 and 630.0 nm in Ny‐Ålesund, Svalbard

Abstract

A survey of dayside 557.7 and 630.0 nm auroral emission, acquired from the all‐sky imagers at the Yellow River Station in Ny‐Ålesund, Svalbard, shows that the dayside auroral oval could be divided into five auroral active regions: the dawnside (Da, 06:00–07:30 MLT) and duskside (Du, 15:30–17:00 MLT) green aurora sectors, the prenoon (W, 07:30–10:00 MLT) and postnoon (H, 13:00–15:30 MLT) peaks for 557.7 and 630.0 nm auroral emissions, and the midday gap (M, 10:00–13:00 MLT) for green aurora. The 630.0 nm intensities in W, M, and H nearly increase linearly with the Kan‐Lee electric field. The 630.0 nm auroral emissions in W and H show a double‐peak feature associated with the change of interplanetary magnetic field (IMF) clock angle: one peak at 90° and the other at 270°. The 630.0 nm emission in M, however, is dominantly excited during the clock angle of 90°–270°. It is considered that the 630.0 nm emissions in W/H and M are related to the prenoon/postnoon antiparallel reconnection at the high‐latitude magnetopause and the subsolar component reconnection, respectively. Moreover, the 630.0 nm intensity in the dayside oval shows the monotonic increase with the absolute value of the north‐south oriented electric field (Ez), but the increasing rate of the intensity in the postnoon (prenoon) oval is larger than that in the prenoon (postnoon) oval when IMF By is negative (positive). Only the 557.7 nm intensity in region M and H/Du increases gradually with the absolute value of negative Ez. These features should be associated with the change of interhemispheric currents produced by Ez.