Determination of the Equatorial Electron Differential Flux From Observations at Low Earth Orbit
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Abstract 
Variations in the highenergy relativistic electron flux of the radiation belts depend on transport, acceleration, and loss processes, and importantly on the lowerenergy seed population. However, data on the seed population is limited to a few satellite missions. Here we present a new method that utilizes data from the Medium Energy Proton/Electron Detector on board the lowaltitude Polar Operational Environmental Satellites to retrieve the seed population at a pitch angle of 90\textdegree. The integral flux values measured by Medium Energy Proton/Electron Detector relate to a low equatorial pitch angle and were converted to omnidirectional flux using parameters obtained from fitting one or two urn:xwiley:jgra:media:jgra54628:jgra54628math0001 functions to pitch angle distributions given by three and a half years of Van Allen Probes data. Two methods to convert from integral to differential flux are explored. One utilizes integral and differential flux energy distributions from the AE9 model, the second employs an iterative fitting approach based on a Reverse Monte Carlo (RMC) method. The omnidirectional differential flux was converted to an equatorial pitch angle of 90\textdegree, again using statistical pitch angle distributions from Van Allen Probe data. We validate the resulting 90\textdegree flux for 100 to 600keV electrons against measurements from the Van Allen Probes and show an average agreement within a factor of 4 for L* > 3.7. The resulting data set offers a high time resolution, across multiple magnetic local time planes, and may be used to formulate eventspecific lowenergy boundary conditions for radiation belt models.

Year of Publication 
2018

Journal 
Journal of Geophysical Research: Space Physics

Date Published 
11/2018

URL 
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025786

DOI 
10.1029/2018JA025786
