Drift Orbit Bifurcations and Cross‐Field Transport in the Outer Radiation Belt: Global MHD and Integrated Test‐Particle Simulations. Issue 10 (30th September 2021)

• Record Type: Journal Article
• Authors: 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.; Chittenden, J. P.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 10(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-30
• Subjects: Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA029802
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Energetic particle fluxes in the outer magnetosphere present a significant challenge to modeling efforts as they can vary by orders of magnitude in response to solar wind driving conditions. In this study, we demonstrate the ability to propagate test particles through global magnetohydrodynamic (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 appear 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. Key Points: We develop high precision test particle simulations integrated inside global magnetohydrodynamic simulations and study drift orbit bifurcations The resulting transport displays notable structure close to the magnetopause and differences for southward and northward interplanetary magnetic field orientations The convection electric field not included in previous DOB studies has a significant effect on the resultant transport characteristics