Solar Fast Wind Regions as Sources of Gradual 20 MeV Solar Energetic Particle Events

Abstract

Abstract : If production of solar energetic particles (SEPs) near the Sun is due to shocks driven by coronal mass ejections (CMEs), then SEP acceleration in slow rather than fast solar wind streams should be favored because both the Alfven and solar wind flow speeds are higher in the fast wind streams. We identify SOHO LASCO fast west-limb or halo CMEs that occurred when the Earth was in fast wind streams indicated by low values of the solar wind 07/06 ratios from the ACE satellite. Those CMEs would be expected to be associated with fewer or weaker SEP events than comparable CMEs in slow wind regions. However, we find no differences between the fast CMEs in fast wind and the fast CMEs in slow wind in terms of their associated SEP intensities or SEP-associated CME speeds.