Drift Orbit Bifurcations and Cross‐field Transport in the Outer Radiation Belt: Global MHD and Integrated Test‐Particle Simulations

R. T. Desai*, J. P. Eastwood, R. B. Horne, H. J. Allison, O. Allanson, C. E. J. Watt, J. W. B. Eggington, S. A. Glauert, N. P. Meredith, M. O. Archer, F. A. Staples, L. Mejnertsen, J. K. Tong, J. P. Chittenden

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Energetic particle fluxes in the outer magnetosphere present a significant challenge to modelling efforts as they can vary by orders of magnitude in response to solar wind driving conditions. In this article, we demonstrate the ability to propagate test particles through global MHD simulations to a high level of precision and use this to map the cross-field radial transport associated with relativistic electrons undergoing drift orbit bifurcations (DOBs). The simulations predict DOBs primarily occur within an Earth radius of the magnetopause loss cone and appears significantly different for southward and northward interplanetary magnetic field orientations. The changes to the second invariant are shown to manifest as a dropout in particle fluxes with pitch angles close to urn:x-wiley:21699380:media:jgra56753:jgra56753-math-0001 and indicate DOBs are a cause of butterfly pitch angle distributions within the night-time sector. The convective electric field, not included in previous DOB studies, is found to have a significant effect on the resultant long term transport, and losses to the magnetopause and atmosphere are identified as a potential method for incorporating DOBs within Fokker-Planck transport models.
Original languageEnglish
Article numbere2021JA029802
Number of pages14
JournalJournal of Geophysical Research: Space Physics
Volume126
Issue number10
Early online date30 Sep 2021
DOIs
Publication statusPublished - Oct 2021

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