loading page

Simulated Trapping of Solar Energetic Protons for the 8-10 March 2012 Geomagnetic Storm: Impact on Inner Zone Protons as Measured by Van Allen Probes
  • +3
  • Mary K. Hudson,
  • Miles Ansley Engel,
  • Brian T. Kress,
  • Zhao Li,
  • Maulik Patel,
  • Richard S. Selesnick
Mary K. Hudson
Dartmouth College

Corresponding Author:mary.k.hudson@dartmouth.edu

Author Profile
Miles Ansley Engel
Los Alamos National Laboratory
Author Profile
Brian T. Kress
NOAA - National Centers for Environmental Information (NCEI)
Author Profile
Zhao Li
Dartmouth College
Author Profile
Maulik Patel
High Altitude Observatory
Author Profile
Richard S. Selesnick
Air Force Research Laboratory
Author Profile


Solar Energetic Protons (SEPs) have been shown to contribute significantly to the inner zone trapped proton population for energies < 100 MeV and L > 1.3 (Selesnick et al., 2007). The Relativistic Electron Proton Telescope (REPT) on the Van Allen Probes launched 30 August 2012 observed a double-peaked (in L) inner zone population throughout the 7-year lifetime of the mission. It has been proposed that a strong SEP event accompanied by a CME-shock in early March 2012 provided the SEP source for the higher L trapped proton population, which then diffused radially inward to be observed by REPT at L ~ 2. Here, we follow trajectories of SEP protons launched isotropically from a sphere at 7 Re in 15s cadence fields from an LFM-RCM global MHD simulation driven by measured upstream solar wind parameters. The timescale of the interplanetary shock arrival is captured, launching a magnetosonic impulse propagating azimuthally along the dawn and dusk flanks inside the magnetosphere, shown previously to produce SEP trapping. The MHD-test particle simulation uses GOES proton energy spectra to weight the initial radial profile required for the radial diffusion calculation over the following two years. GOES proton measurements also provide a dynamic outer boundary condition for radial diffusion. A direct comparison with REPT measurements 20 months following the trapping event in March 2012 provides good agreement with this novel combination of short-term and long-term evolution of the newly trapped protons.