The magnetic local time distribution of energetic electrons in the radiation belt region

Allison, Hayley J. ORCID: https://orcid.org/0000-0002-6665-2023; Horne, Richard B. ORCID: https://orcid.org/0000-0002-0412-6407; Glauert, Sarah A. ORCID: https://orcid.org/0000-0003-0149-8608; Del Zanna, Giulio. 2017 The magnetic local time distribution of energetic electrons in the radiation belt region. Journal of Geophysical Research:Space Physics, 122 (8). 8108-8123. https://doi.org/10.1002/2017JA024084

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Abstract/Summary

Using 14 years of electron flux data from the National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites, a statistical study of the magnetic local time (MLT) distribution of the electron population is performed across a range of activity levels, defined by AE, AE*, Kp, solar wind velocity (Vsw), and VswBz. Three electron energies (>30, >100, and >300 keV) are considered. Dawn-dusk flux asymmetries larger than order of magnitude were observed for >30 and >100 keV electrons. For >300 keV electrons, dawn-dusk asymmetries were primarily due to a decrease in the average duskside flux beyond L* ∼ 4.5 that arose with increasing activity. For the >30 keV population, substorm injections enhance the dawnside flux, which may not reach the duskside as the electrons can be on open drift paths and lost to the magnetopause. The asymmetries in the >300 keV population are attributed to the combination of magnetopause shadowing and >300 keV electron injections by large electric fields. We suggest that 3-D radiation belt models could set the minimum energy boundary (Emin) to 30 keV or above at L* ∼ 6 during periods of low activity. However, for more moderate conditions, Emin should be larger than 100 keV and, for very extreme activities, ∼300 keV. Our observations show the extent that in situ electron flux readings may vary during active periods due to the MLT of the satellite and highlight the importance of 4-D radiation belt models to fully understand radiation belt processes.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1002/2017JA024084
Programmes:	BAS Programmes > BAS Programmes 2015 > Space Weather and Atmosphere
ISSN:	0148-0227
Additional Keywords:	energetic electrons, magnetic local time, electrons distribution, radiation belts
Date made live:	06 Sep 2017 09:04 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/516369

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