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Examination of Radiation Belt Dynamics during Substorm Clusters: Activity Drivers and Dependencies of Trapped Flux Enhancements

Rodger, CJ; Hendry, AT; Clilverd, MA; Forsyth, C; Morley, SK; (2022) Examination of Radiation Belt Dynamics during Substorm Clusters: Activity Drivers and Dependencies of Trapped Flux Enhancements. Journal of Geophysical Research: Space Physics , 127 (1) , Article e2021JA030003. 10.1029/2021ja030003.

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JGR Space Physics - 2021 - Rodger - Examination of Radiation Belt Dynamics during Substorm Clusters Activity Drivers and.pdf - Accepted Version
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Abstract

Dynamical variations of radiation belt trapped electron fluxes are examined to better understand the variability of enhancements linked to substorm clusters. Analysis is undertaken using the Substorm Onsets and Phases from Indices of the Electrojet substorm cluster algorithm for event detection. Observations from low earth orbit are complemented by additional measurements from medium earth orbit to allow a major expansion in the energy range considered, from medium energy energetic electrons up to ultra-relativistic electrons. The number of substorms identified inside a cluster does not depend strongly on solar wind drivers or geomagnetic indices either before, during, or after the cluster start time. Clusters of substorms linked to moderate (100 nT < AE ≤ 300 nT) or strong AE (AE ≥ 300 nT) disturbances are associated with radiation belt flux enhancements, including up to ultra-relativistic energies by the strongest substorms (as measured by strong southward Bz and high AE). These clusters reliably occur during times of high speed solar winds streams with associated increased magnetospheric convection. However, substorm clusters associated with quiet AE disturbances (AE ≤ 100 nT) lead to no significant chorus whistler mode intensity enhancements, or increases in energetic, relativistic, or ultra-relativistic electron flux in the outer radiation belts. In these cases the solar wind speed is low, and the geomagnetic Kp index indicates a lack of magnetospheric convection. Our study clearly indicates that clusters of substorms occurring outside of high speed wind streams are not by themselves sufficient to drive acceleration, which may be due to the lack of pre-cluster convection.

Type: Article
Title: Examination of Radiation Belt Dynamics during Substorm Clusters: Activity Drivers and Dependencies of Trapped Flux Enhancements
DOI: 10.1029/2021ja030003
Publisher version: https://doi.org/10.1029/2021JA030003
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.
Keywords: radiation belt electrons; radiation belt acceleration; magnetospheric substorm; magnetospheric convection; whistler mode chorus
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10141106
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