Challenging the Use of Ring Current Indices During Geomagnetic Storms

Jasmine Sandhu*, Jonathan Rae, Maria-Theresia Walach

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
13 Downloads (Pure)

Abstract

The ring current experiences dramatic enhancements during geomagnetic storms, however understanding the global distribution of ring current energy content is restricted by spacecraft coverage. Many studies use ring current indices as a proxy for energy content, but these indices average over spatial variations and include additional contributions. We have conducted an analysis of Van Allen Probes’ data, identifying the spatial distribution and storm-time variations of energy content. Ion observations from the HOPE and RBSPICE instruments were used to estimate energy content in L-MLT bins. The results show large enhancements particularly in the premidnight sector during the main phase, alongside reductions in local time asymmetry and intensity during the recovery phase. A comparison with estimated energy content using the Sym-H index was conducted. In agreement with previous results, the Sym-H index significantly overestimates (by up to ∼ 4 times) the energy content, and we attribute the difference to contributions from additional current systems. A new finding is an observed temporal discrepancy, where energy content estimates from the Sym-H index maximise 3 to 9 hours earlier than in situ observations. Case studies reveal a complex relationship, where variable degrees of agreement between the Sym-H index and in situ measurements are observed. The results highlight the drawbacks of ring current indices and emphasise the variability of the storm time ring current.
Original languageEnglish
Article numbere2020JA028423
Number of pages19
JournalJournal of Geophysical Research: Space Physics
Volume126
Issue number2
Early online date10 Feb 2021
DOIs
Publication statusPublished - Feb 2021

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