Position of the Energetic Electron Trapping Boundary Relative to Auroral Oval Boundaries during the Magnetic Storm on December 19–22, 2015, Based on Data from the Meteor-M2 Satellite

Abstract

This paper studies the position of the trapping boundary of electrons with energies of >100 keV relative to the equatorial boundary of the auroral oval during a large magnetic storm on December 19–22, 2015, with a minimum Dst of –170 nT as measured by the Meteor-M2–1 satellite. Energetic electrons with energies from 0.1 to 13 MeV and fluxes of low-energy electrons with energies from 0.13 to 16.64 keV have been measured. It is taken into account that the pitch-angle distribution of energetic electrons near the trapping boundary is almost isotropic. It is shown that the energetic electron trapping boundary during the considered storm is detected inside the auroral oval or near its polar boundary. The distance along the geomagnetic latitude between the energetic electron trapping boundary and the equatorial boundary of the auroral oval is determined. The dependence of this distance on time for crossings of the oval before and after midnight is analyzed. It is shown that the distance between the trapping boundary and the equatorial boundary of the oval during the storm decreases after midnight and increases before midnight. These values are almost equal near minimum Dst. The significance of the results obtained for a description of changes in the magnetospheric topology during magnetic storms is discussed.