Wednesday

Flare/Coronal Mass Ejection (CME) events originating in Active Regions can accelerate protons to relativistic energies. These particles may produce signatures at Earth detected by neutron monitors as Ground Level Enhancements (GLEs), as well as photon emission associated with interaction with solar plasmas, including gamma-ray emission. Interest in the acceleration and propagation of protons in the ~100 MeV - ~1 GeV energy range has been renewed by recent observations by PAMELA and FERMI LAT. While traditional proton propagation models used to interpret GLE events solve a spatially 1D focused transport equation, there is evidence that at relativistic energies 3D processes such as drift and heliospheric current sheet effects are important. By means of a 3D test particle model we integrate trajectories of relativistic solar protons through interplanetary space and show that the spatial extent of the event at 1 AU is larger than the footprint of the injection region near the Sun. We discuss the dependence of the number of times particles cross 1 AU on the polarity of the interplanetary magnetic field, for a given mean free path. The latter quantity is important when comparing gamma-ray flare data with SEP fluxes measured in space. We also simulate particle spectra and intensity profiles and compare them with PAMELA observations for the GLE event of 2012 May 17.