Authors: Matthew West (Southwest Research Institute), Federica Frassati (National Institute of Astrophysics - Astrophysical Observatory of Turin), Monica Laurenza (Istituto di Astrofisica e Planetologia Spaziali), Alessandro Bemporad (National Institute of Astrophysics - Astrophysical Observatory of Turin), Salvatore Mancuso (National Institute of Astrophysics - Astrophysical Observatory of Turin), Roberto Susino (National Institute of Astrophysics - Astrophysical Observatory of Turin), Tommaso Alberti (Istituto di Astrofisica e Planetologia Spaziali), Paolo Romano (National Institute of Astrophysics - Osservatorio Astrofisico di Catania)
The acceleration of high-energy particles at the Sun is an intriguing unsolved problem. The acceleration of so-called solar energetic particles (SEPs) from suprathermal energies up to relativistic energies is believed to occur during solar eruptions at flare sites, and at shock waves driven by coronal mass ejections (CMEs). This presentation summarizes a study of the 2013 June 21 prominence eruption, that was accompanied by an M2.9 class flare, a fast CME, a weak and subcritical shock, and type III and II radio bursts. The relationship between the expanding front, coronal streamers, and the SEP fluxes observed at different locations is investigated, with an emphasis on the streamer deflection in the lower and middle corona. The obtained results provide evidence, for the first time, that the interaction between an expanding front and streamer structures can be responsible for the acceleration of high-energy SEPs up to at least 100 MeV, as it favors particle trapping and hence increases the shock acceleration efficiency.