Statistical Evidence for Contributions of Flares and Coronal Mass Ejections to Major Solar Energetic Particle Events

Solar energetic particle (SEP) events are related to flares and coronal mass ejections (CMEs). This work is a new investigation of statistical relationships between SEP peak intensities - deka-MeV protons and near-relativistic electrons - and characteristic quantities of the associated solar activity. We consider the speed of the CME and quantities describing the flare-related energy release: peak flux and fluence of soft X-ray (SXR) emission and the fluence of microwave emission. The sample comprises 38 SEP events associated with strong SXR bursts (classes M and X) in the western solar hemisphere between 1997 and 2006, in which the flare-related particle acceleration was accompanied by radio bursts indicating electron escape into the interplanetary space. The main distinction of the present statistical analysis from earlier work is that in addition to the classical Pearson correlation coefficient, the partial correlation coefficients are calculated to remove the correlation effects between the solar parameters themselves. The classical correlation analysis shows the usual picture of correlations with broad scatter between SEP peak intensities and the different parameters of solar activity and strong correlations between the solar activity parameters themselves. The partial correlation analysis shows that the only parameters that significantly affect the SEP intensity are the CME speed and the SXR fluence. The SXR peak flux and the microwave fluence make no additional contribution. We conclude that these findings bring statistical evidence that both flare acceleration and CME shock acceleration contribute to the deka-MeV proton and near-relativistic electron populations in large SEP events.