Drift orbit bifurcations and cross-field transport in the outer radiation belt: global MHD and integrated test-particle simulations
File(s)
Published version
Author(s)
Type
Journal Article
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 90◦
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.
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 90◦
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.
Date Issued
2021-10
Date Acceptance
2021-09-04
Citation
Journal of Geophysical Research: Space Physics, 2021, 126 (10), pp.1-14
ISSN
2169-9380
Publisher
American Geophysical Union
Start Page
1
End Page
14
Journal / Book Title
Journal of Geophysical Research: Space Physics
Volume
126
Issue
10
Copyright Statement
© 2021. The Authors.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Sponsor
Natural Environment Research Council (NERC)
Engineering & Physical Science Research Council (EPSRC)
UKRI
Natural Environment Research Council (NERC)
Identifier
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JA029802
Grant Number
NE/P017347/1
EP/T01735X/1
EP/T01735X/1
NE/P017142/1
Subjects
physics.space-ph
physics.space-ph
astro-ph.EP
astro-ph.IM
physics.comp-ph
physics.plasm-ph
0201 Astronomical and Space Sciences
0401 Atmospheric Sciences
Publication Status
Published
Date Publish Online
2021-09-17