Several Hundred keV electron precipitation measured by Korean satellite STSAT-1

In this presentation, we show two kinds of electron precipitations observed by the Korean satellite STSAT-1. One is microburst that has very short duration of less than 1 second. Our observations show microburst energy spectra of precipitated electrons inside the loss cone (precipitated) have higher e-folding energies during disturbed times than quiet times. The loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast pitch angle diffusion requires diffusion coefficients be larger than ~3.5 ×10-2 rad2/sec, while ~1.5 ×10-5 rad2/sec was proposed by Albert (2002). The other precipitation has long duration of a few hours at the midnight trapping boundary. These events occur under quiet geomagnetic condition and display energy dispersion in the low latitude boundary. We have modeled this precipitation form invoking pitch angle scattering in the field reversal region where magnetic field significantly varies within a cyclotron radius and the first adiabatic invariant is not conserved. Our observations show these two kinds of precipitation could be the dominant loss mechanism of relativistic electrons in the radiation belt.