Solar Energetic Proton Access and Trapping in the Inner Magnetosphere
Abstract
While galactic cosmic rays striking the atmosphere and producing neutron decay provide the primary source (Cosmic Ray Albedo Neutron Decay) of the more energetic component of inner zone protons, Solar Energetic Protons (SEPs) have been shown to contribute significantly to the inner zone trapped proton population for energies less than 100 MeV and L greater than 1.3 (Selesnick et al., 2007). Both time-stepped empirical Tsyganenko-Sitnov and Lyon-Fedder-Mobarry MHD simulations, driven by L1 solar wind input available from OMNIweb, will be used as field models to calculate cutoff suppression and trapping of SEPs with the rbelt3D particle tracing code developed at Dartmouth. A novel combination of MHD-test particle simulations of SEP trapping followed by a radial diffusion calculation over the following 1-2 years will be implemented, using a diffusion code developed by Li et al. (2017) with a diffusion coefficient optimized by Selesnick and Albert (2019) to match Van Allen Probes measurements. A strong SEP event in March 2012 (the strongest of Solar Cycle 24) which preceded the launch of Van Allen Probes will be used as a test case for the two-timescale model of SEP trapping and inward diffusion, comparing directly with measurements from the Relativistic Electron Proton Telescope on Van Allen Probes. GOES 13 and 15 Energetic Particle Sensor measurements provide an outer boundary condition for the radial diffusion calculation as well as initial test-particle weighting, based on the interplanetary solar proton spectrum, for the MHD-test particle simulations. Further investigation of cutoff suppression (Qin et al., 2019; Li et al., 2021), its relationship to trapping and their energy dependences will be investigated along with modification of the outer boundary of the inner zone, and the effects of an inductive electric field obtained directly from the MHD field model and from time-stepping magnetic
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 07, 2024
- Source ID
- FA95502310629
Entities
People
- M. K. Hudson
Organizations
- Air Force Office of Scientific Research
- Board of Trustees of Dartmouth College
- United States Air Force