Storm-Time Ring Current and Plasma Sheet Dynamics from IMAGE/HENA Energetic Neutral Atom Observations

Abstract:

Energetic neutral atom (ENA) imaging has emerged as a powerful method for global characterization of the inner magnetosphere. Generated by charge-exchange collisions between energetic magnetospheric ions and cold neutral atoms of the geocorona, ENA emissions can be used to remotely sense energetic ion distribution whose non-thermal pressure dominates the dynamics of the inner magnetosphere. In this work, we examine storm-time temporal and spatial variation of energetic ion distribution in the ring current and plasma sheet based on measurements from High Energetic Neutral Atom (HENA) previously on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite. To this end, we conduct a comprehensive statistical analysis of HENA data by employing constrained linear inversion techniques that allow for specification of distribution of energetic hydrogen ions as a function of MLT and L-shell during geomagnetically disturbed periods. To enable the applicability of the inversion methodology to the whole data sets we employ “parameter tuning” techniques that will systematically select an optimal set of parameters for individual inversions.