A1 Refereed original research article in a scientific journal
Solar interacting protons versus interplanetary protons in the core plus halo model of diffusive shock acceleration and stochastic re-acceleration
Authors: Kocharov L, Laitinen T, Vainio R, Afanasiev A, Mursula K, Ryan JM
Publisher: IOP PUBLISHING LTD
Publication year: 2015
Journal: Astrophysical Journal
Journal name in source: ASTROPHYSICAL JOURNAL
Journal acronym: ASTROPHYS J
Article number: ARTN 80
Volume: 806
Issue: 1
First page : 1
Last page: 11
Number of pages: 11
ISSN: 0004-637X
DOI: https://doi.org/10.1088/0004-637X/806/1/80
With the first observations of solar gamma-rays from the decay of pions, the relationship of protons producing ground level enhancements (GLEs) on the Earth to those of similar energies producing the gamma-rays on the Sun has been debated. These two populations may be either independent and simply coincident in large flares, or they may be, in fact, the same population stemming from a single accelerating agent and jointly distributed at the Sun and also in space. Assuming the latter, we model a scenario in which particles are accelerated near the Sun in a shock wave with a fraction transported back to the solar surface to radiate, while the remainder is detected at Earth in the form of a GLE. Interplanetary ions versus ions interacting at the Sun are studied for a spherical shock wave propagating in a radial magnetic field through a highly turbulent radial ray (the acceleration core) and surrounding weakly turbulent sector in which the accelerated particles can propagate toward or away from the Sun. The model presented here accounts for both the first-order Fermi acceleration at the shock front and the second-order, stochastic re-acceleration by the turbulence enhanced behind the shock. We find that the re-acceleration is important in generating the gamma-radiation and we also find that up to 10% of the particle population can find its way to the Sun as compared to particles escaping to the interplanetary space.