GC2022-STP018

Stable auroral red (SAR) arcs are the consequence of interaction of energetic ions of the ring current with the plasmapause. The literature is dominated by the idea that stable auroral red arcs are observed during the recovery phase of magnetic storms. Our previous studies of the subauroral luminosity at the Yakutsk meridian showed that SAR arcs appear and/or brightening during the substorm expansion phase. This work presents for the first time the results of simultaneous observations with all-sky imagers of aurora dynamics at the Zhigansk station (CGMLat 62°, CGMLon 196°) and formation of the SAR arc at the subauroral Maimaga station (CGMLat 58°, CGMLon 202°). The event of February 15, 2018, with a minimum of SYM-H = –20 nT, in which the substorm growth phase occurred after the IMF Bz southward turn, is considered. The expansion phase of this substorm began in the evening sector of 2000–2200 MLT with further extension of the auroral bulge in the MLT postmidnight hours, where the brightening of red arc from the western horizon to the east near the diffuse aurora (DA) boundary was observed. At the same time, there was also an eastward motion of the glow ledges on the polar edge of the SAR arc, the rays (corona) appeared and the luminosity pulsations were registered in the vicinity of the DA boundary in the 557.7 nm emission.

The measurement aboard SWARM-B satellite of the subauroral electron temperature peaks verify ground-based SAR arc observations during the growth and recovery phases of the substorm. We believe that the dynamics of discrete and diffuse aurorae, as well as SAR arc in this event mapped such magnetospheric phenomena as: the convection enhancement; the eastward extension of substorm injection region; the eastward overlap of asymmetric ring current with the outer plasmasphere; the electric eastward drift of cold plasma, the intensification of zone 2 small-scale (~10 km) field-aligned current and the pulsating precipitation of energetic electrons in the plasmapause vicinity. This research was supported in part by the Russian Foundation for Basic Research, project no. 21-55-50013.