Large-scale coronal disturbances and angular spread of SEP events

We discuss the currently available observations and tools to understand the angular spread of solar energetic particle (SEP) events in the corona. Following the widely used classification scheme of SEP events, large gradual SEP events, accelerated by CME-driven shocks, are expected to have much larger angular spreads than small impulsive SEP events that are thought to be due to impulsive solar flares. But some SEP events, labeled as impulsive, are observed at locations several tens of degrees away from the longitudes that are usually conceived as well-connected. One possibility is that large-scale disturbances from the flare/CME site can transport energetic particles to locations that are well-connected to Earth. Another possibility is that magnetic field in the corona undergoes significant excursions before it reaches the height above which it approximately follows the Parker spiral. In order to evaluate relative importance of the two possibilities, we re-examine the archive of SOHO EIT data to study the association of SEP events during cycle 23 with EIT waves, and conduct global magnetic field extrapolation using the potential field source surface (PFSS) model. We also study recent SEP events whose source regions were observed by STEREO EUVI and/or SDO AIA. Images from AIA, in particular, have revealed more EUV waves from flares and CMEs than EIT would have, largely because of the improvement in cadence and sensitivity. This makes it possible for us to clarify the role of large-scale coronal disturbances in the angular spread of SEP events.