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A distributed lag-autoregressive model of geostationary relativistic electron fluxes: comparing the influences of waves, seed and source electrons, and solar wind inputs

Simms, Laura; Engebretson, Mark; Clilverd, Mark ORCID: https://orcid.org/0000-0002-7388-1529; Rodger, Craig; Lessard, Marc; Gjerloev, Jesper; Reeves, Geoffrey. 2018 A distributed lag-autoregressive model of geostationary relativistic electron fluxes: comparing the influences of waves, seed and source electrons, and solar wind inputs. Journal of Geophysical Research: Space Physics, 123 (5). 3646-3671. https://doi.org/10.1029/2017JA025002

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Abstract/Summary

Relativistic electron flux at geosynchronous orbit depends on enhancement and loss processes driven by ULF Pc5, chorus, and EMIC waves, seed electron flux, magnetosphere compression, the "Dst effect", and substorms, while solar wind inputs such as velocity, number density, and IMF Bz drive these factors and thus correlate with flux. Distributed lag regression models show the time delay of highest influence of these factors on log10 high energy electron flux (0.7 – 7.8 MeV, LANL satellites). Multiple regression with an autoregressive term (flux persistence) allows direct comparison of the magnitude of each effect while controlling other correlated parameters. Flux enhancements due to ULF Pc5 and chorus waves are of equal importance. The direct effect of substorms on high energy electron flux is strong, possibly due to injection of high energy electrons by the substorms themselves. Loss due to EMIC waves is less influential. Southward Bz shows only moderate influence when correlated processes are accounted for. Adding covariate compression effects (pressure and IMF magnitude) allows wave‐driven enhancements to be more clearly seen. Seed electrons (270 keV) are most influential at lower relativistic energies, showing that such a population must be available for acceleration. However, they are not accelerated directly to the highest energies. Source electrons (31.7 keV) show no direct influence when other factors are controlled. Their action appears to be indirect via the chorus waves they generate. Determination of specific effects of each parameter when studied in combination will be more helpful in furthering modelling work than studying them individually.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1029/2017JA025002
ISSN: 21699380
Date made live: 25 Apr 2018 09:16 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/519881

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