OBSERVATIONS OF SUBSTORM ACTIVITY FROM THE DATA OF MAIN CAMERA SYSTEM AND THD SATELLITE IN THE PLASMA SHEET

Abstract

We investigated an interesting case of the space-time dynamics of substorm activations (AL ~ 800 nT) on December 24, 2014, when there were simultaneous observations on the THEMIS D satellite in the plasma sheet (|X| ~ 6.2 RE) and ground-based observations on the Kola Peninsula. The development of the substorm activity in the interval of ~ 19:00 to ~ 20:00 UT was considered. In this interval, at Lovozero station (LOZ), three peaks in the Pi1B pulsations were recorded, associated with the brightening of arcs near LOZ. The first peak was observed in connection with the appearance of beads structures in the auroras along the growth phase arc to the south from LOZ latitude. The second and third peaks in Pi1B pulsations were associated with the expansion phase, when three dipolarization fronts (DFs) were registered according THD data. DFs and injection of energetic electrons into the magnetosphere were observed near the moments of sudden intensification of auroras: brightening of arcs, breakup in aurora. Besides, it was shown that the development of substorm occurs near the Harang discontinuity (HD) according to the IMAGE magnetometers data. In this case, we can follow the development of aurora around the HD according to the data of the all sky camera in Apatity. It was shown that the pre-onset auroral forms were moved accordingly the two-cell ionospheric convection developed during the growth phase of the substorm.