Experiment of ~200 keV electron pitch angle diffusion near loss cone boundary.

Abstract:

In this presentation, we show the ~200 keV electron pitch angle distribution near loss cone boundary and derive the minimum pitch angle diffusion coefficients calculated from the observation. Solid-state detectors aboard low altitude satellite, STSAT-1, were used for the measurements of the electron energy spectra. In order to measure the pitch angle distribution, we rotated the satellite’s attitude about 90° with respect to the geomagnetic field line. The results show sharp boundary at the loss cone angle of 55°. To demonstrate the pitch angle distribution, we simulated drift loss and diffusion effect for longitude by solving the diffusion equation. While the pitch angle distribution measurements were performed at the altitude of 700 km, latitude of 70° and longitude of 130°E, the drift electrons are lost in the SAA region. Accordingly, the observed electrons are results of pitch angle diffusion from loss cone boundary and we can estimate minimum diffusion coefficient. In our model, the pitch angle diffusion coefficient should be larger than 1.0x10⁵ rad²/sec