Paper detail

Latitudinal Connectivity of Ground Level Enhancement Events

We examined the source regions and coronal environment of the historical ground level enhancement (GLE) events in search of evidence for non-radial motion of the associated coronal mass ejection (CME). For the 13 GLE events that had source latitudes >30 degrees we found evidence for possible non-radial CME motion due to deflection by large-scale magnetic structures in nearby coronal holes, streamers, or pseudo streamers. Polar coronal holes are the main source of deflection in the rise and declining phases of solar cycles. In the maximum phase, deflection by large-scale streamers or pseudo streamers overlying high-latitude filaments seems to be important. The B0 angle reduced the ecliptic distance of some GLE source regions and increased in others with the net result that the average latitude of GLE events did not change significantly. The non-radial CME motion is the dominant factor that reduces the ecliptic distance of GLE source regions, thereby improving the latitudinal connectivity to Earth. We further infer that the GLE particles must be accelerated at the nose part of the CME-driven shocks, where the shock is likely to be quasi-parallel.