The features of the auroral topside ionosphere-magnetosphere coupling induced by the time-dependent magnetic field

Abstract

It has been revealed in numerous studies that the topside auroral ionosphere is an important source of ions for the magnetosphere (e. g. /1/). The transport of ionospheric ions couples the auroral ionosphere and the near-equatorial regions. The source intensity and the coupling is strongest during substorms when at least three types of magnetospheric field reconfiguration occur in the equatorial region: stretching, collapse and oscillations. In this study the transport of the ionospheric oxygen ions is investigated by tracing their motion in the time-dependent magnetic field modeled for stretching and collapse type reconfigurations. Different types of orbits are obtained depending on the initial particle characteristics (energy, pitch angle, position) and on the temporal and spatial changes of the field. The ionospheric oxygen ion population is energized up to tens of keV energy range. Final pitch angle values are confined in narrow cones around 0° and 180°. The energetic and collimated ionospheric component couples the south and north ionospheres and can contribute to the cross-tail current changes during substorms.