Quantifying energetic electron loss from current sheet scattering at the outermost boundary of the outer radiation belt

Abstract:

During magnetically active periods, field lines in the nightside outer radiation belt become highly stretched. Here, at the outermost boundary (~9 to ~10 Earth radii), field line curvature within the current sheet can break conservation of the magnetic moment of energetic electrons (≳50 keV). When these electrons pass through this region, they experience a quasi-random change in their magnetic moment that has the potential to scatter them into the loss cone. Recently, it was suggested by Sivadas et al. (2019) that this process, known as current sheet scattering, significantly contributes to the loss of energetic electrons during the substorm growth phase. Using relativistic single particle tracking in empirical magnetosphere models, we examine such an event and quantify the expected loss rates due to current sheet scattering. We compare our results to conjugate observations from THEMIS satellites and Poker Flat Incoherent Scatter Radar (PFISR). Preliminary analysis suggests a per second loss rate of 0.1% for electrons near 1 MeV. This implies substantial dropouts ~50% when the tail is stretched for tens of minutes during substorm growth phases.