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

Desai, R. T., Eastwood, J. P., Horne, R. B., Allison, H. J., Allanson, O., Watt, C. E. J., Eggington, J. W. B., Glauert, S. A., Meredith, N. P., Archer, M. O., Staples, F. A., Mejnertsen, L., Tong, J. K. and Chittenden, J. P. (2021) Drift Orbit Bifurcations and Cross‐field Transport in the Outer Radiation Belt: Global MHD and Integrated Test‐Particle Simulations. Journal of Geophysical Research: Space Physics, 126 (10). e2021JA029802. ISSN 2169-9380

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Official URL: https://doi.org/10.1029/2021ja029802


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.

Item Type: Article
Additional Information: Funding information: RTD, JPE, and JPC acknowledge fund-ing from NERC grant NE/P017347/1 (Rad-Sat). HJA is supported by an Alexander Von Humboldt fellowship. OA is supported by a NERC Inde-pendent Research Fellowship NE/V013963/1. CEJW acknowledges grants NE/V002759/2 and ST/W002078/1. MOA holds a UKRI (STFC/EPSRC) Stephen Hawking Fellowship EP/T01735X/1. JWBE is supported by Grant NE/P017142/1 (SWIGS). RH, SG, and NM would like to acknowledge the Natural Environment Research Council Highlight Topic grant NE/P10738X/1 (Rad-Sat) and the NERC grants NE/V00249X/1 298 (Sat-Risk) and NE/R016038/1
Uncontrolled Keywords: Energetic particles: trapped, Interactions with particles and fields, MAGNETOSPHERIC PHYSICS, Magnetosheath, PLANETARY SCIENCES: SOLID SURFACE PLANETS, Radiation belts, Research Article, SPACE WEATHER, Space radiation environment
Subjects: F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: John Coen
Date Deposited: 28 Sep 2021 11:21
Last Modified: 20 Oct 2021 14:00
URI: http://nrl.northumbria.ac.uk/id/eprint/47378

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