Statistical analysis of electron lifetimes at GEO: Comparisons with chorus-driven losses

TitleStatistical analysis of electron lifetimes at GEO: Comparisons with chorus-driven losses
Publication TypeJournal Article
Year of Publication2014
AuthorsBoynton, RJ, Balikhin, MA, Mourenas, D
JournalJournal of Geophysical Research: Space Physics
Volume119
Issue8
Pagination6356 - 6366
Date Published08/2014
KeywordsChorus; electron lifetimes; electron losses; oblique waves
AbstractThe population of electrons in the Earth's outer radiation belt increases when the magnetosphere is exposed to high-speed streams of solar wind, coronal mass ejections, magnetic clouds, or other disturbances. After this increase, the number of electrons decays back to approximately the initial population. This study statistically analyzes the lifetimes of the electron at Geostationary Earth Orbit (GEO) from Los Alamos National Laboratory electron flux data. The decay rate of the electron fluxes are calculated for 14 energies ranging from 24 keV to 3.5 MeV to identify a relationship between the lifetime and energy of the electrons. The statistical data show that electron lifetimes increase with energy. Also, the statistical results show a good agreement up to ∼1 MeV with an analytical model of lifetimes, where electron losses are caused by their resonant interaction with oblique chorus waves, using average wave intensities obtained from Cluster statistics. However, above 500 keV, the measured lifetimes increase with energy becomes less steep, almost stopping. This could partly stem from the difficultly of identifying lifetimes larger than 10 days, for high energy, with the methods and instruments of the present study at GEO. It could also result from the departure of the actual geomagnetic field from a dipolar shape, since a compressed field on the dayside should preferentially increase chorus-induced losses at high energies. However, during nearly quiet geomagnetic conditions corresponding to lifetime measurement periods, it is more probably an indication that outward radial diffusion imposes some kind of upper limit on lifetimes of high-energy electrons near geostationary orbit.
URLhttp://doi.wiley.com/10.1002/2014JA019920
DOI10.1002/2014JA019920
Short TitleJ. Geophys. Res. Space Physics


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