| Relativistic electron fluxes in Earth's Van Allen Belts can have severe consequences for space based assets. Much effort has been expended to understand the variability of these fluxes and their acceleration and loss mechanisms. For relativistic electrons in the outer radiation belt, the main loss mechanism appears to be precipitation to Earth's ionosphere although the leading form of this precipitation is still under debate. Relativistic electron microbursts have been studied extensively in the past and are clearly seen in the satellite data whereas duskside relativistic electron precipitation events are not as visible in the satellite data but are the only form of relativistic precipitation seen in balloon data.;The focus of this dissertation is to compare balloon and satellite observations of relativistic electron precipitation, explain and correct the apparent deficit of high energy duskside relativistic electron precipitation events observed in satellite data, and reconcile this with what has been observed by balloons since the INTERBOA balloon mission in 1996. After a review of relevant background material covering the magnetosphere and the radiation belts, the SAMPEX mission is introduced and an analysis of data obtained from 1992 to 2004 is presented. 100 ms cadence data from the HILT detector on board SAMPEX is used to identify candidate events whose spectra are then analyzed by means of the lower time resolution count rates from the PET detector. The results of this analysis show that there exist a form of relativistic electron precipitation distinct from microbursts or bands and that this type of event primarily occurs on the dusk side. In addition to the above analysis, several case studies obtained from the SAMPEX data are presented to support this conclusion. Also presented is a review of the BARREL mission and results obtained to date. BARREL is currently in a development phase and has been conducting test flights since 2008 during which significant progress has been made on mission, payload and ground station design. Not enough events have been observed for a statistical comparison, however, as the science campaigns will not launch until December 2012 and Dec. 2013. |
