Measuring the Pitch-Angle Scattering of Radiation-Belt Electrons as They Drift Across the Plasmaspheric Drainage Plume

English Abstract:

Using the multisatellite SOPA data set of radiation-belt electrons at geosynchronous orbit, the pitch-angle scattering of radiation-belt electrons in plasmaspheric drainage plumes is investigated. When geomagnetic activity is high a plasmaspheric drainage plume flows in the dayside magnetosphere, crossing geosynchronous orbit post noon local time. Radiation-belt electrons drift from dawn to dusk across the dayside magnetosphere and during high geomagnetic activity they drift through the drainage plume. The locations of the drainage plumes are identified with the MPA plasma instrument onboard the geosynchronous satellites and the anisotropy of the radiation-belt electrons is measured upstream (dawnward) and downstream (duskward) of the drainage-plume crossings. Combining the measurements from 5 spacecraft from 126 drainage-plume crossings, statistical analysis of the reduction in anisotropy of the radiation-belt electrons across the drainage plumes yields estimates for the rate of pitch-angle scattering of the electrons within the plumes. The pitch-angle-diffusion coefficients estimated from the scattering measurements are of the magnitude as expected values for EMIC waves in the plume at high electron energies (1.5 MeV) and as expected values for whistler-mode hiss in the plume at lower electron energies (150 keV).