Investigations of the properties of radiation belt electron precipitation observed by the FIREBIRD-II CubeSats

Abstract

High energy electrons can be trapped by the Earth's magnetic field in regions known as the radiation belts. Some of these electrons will impact the upper atmosphere and be lost from the radiation belt system in a process known as electron precipitation. This dissertation explores two questions regarding electron precipitation using data from the focused investigations of relativistic electron burst intensity, range, and dynamics II CubeSat mission. The first question was to determine the energy dependence of specific type of impulsive precipitation known as a microburst, which may be a significant contributer to electron loss from the radiation belts. A statistical study of several hundred microbursts was performed and the energy spectrum was found to generally be exponential with a wide rage of possible parameters depending in part on the level of geomagnetic activity. In addition, comparison of this spectrum with the rest of the radiation belt population revealed that microbursts are a more effective loss mechanism for electrons with relatively lower energies. The second question addresses the possibility of inducing electron precipitation using magnetospheric waves artificially generated by a spacecraft. Waves of 3.0 or 8.2 kHz were excited in the magnetosphere by the Demonstration and Science Experiments satellite and a related signature was searched for in the precipitating electrons. There was no evidence of additional precipitating electrons, so an sensitivity estimate was carried out to place boundaries on the diffusion rates needed to create a measurable precipitation signature. It was found that in many cases a diffusion rate similar to those driven by naturally occurring waves was required, but in cases with a high number of electrons available to interact with the waves the diffusion rates could be orders of magnitude weaker and still produce a measurable amount of precipitation.