Speaker
Dr
Georgia de Nolfo
(NASA/GSFC)
Description
Solar Energetic Particles (SEPs) are accelerated at the Sun in solar flares or by the shocks formed by Coronal Mass Ejections (CMEs). However, the effects of transport en route to Earth often obscures which process dominates, and when. At the highest energies, the effects of transport can be minimal, providing an opportunity to resolve the origin of particle acceleration. The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) instrument provides new and unique observations that can help separate the effects of acceleration and transport. Furthermore, PAMELA bridges a critical gap in energy between space-based and ground-based measurements. We report on the PAMELA observations of the 2012 May 17 ground level enhancement (GLE). PAMELA observations reveal two distinct populations, a low-energy SEP population that exhibits significant scattering or redistribution and a high-energy population that reaches the Earth relatively unaffected by dispersive transport effects. We conclude that the scattering or redistribution at low energies takes place locally revealing effects of SEP transport in the Earth's magnetosphere, in particular, the magnetosheath. The redistribution may derive from large amplitude standing mirror mode waves in the magnetosheath.
Author
Dr
Georgia de Nolfo
(NASA/GSFC)
