A Statistical Study On The Correlation Between Solar Energetic Particle Events And Different Solar Activities

The relationship between the Solar Energetic Particle (SEP) events and the solar activities is an important issue in space weather study. The ssolution to this issue will help to establish a prediction model of the SEP events. In this thesis, in order to understand how these solar activities make their contribution to the acceleration process of SEP, we mainly study the relationships between the large SEP events and the solar activities, such as solar wind speed, solar flare class and Coronal Mass Ejection (CME).A total of68large gradual SEP events from1997to2006were selected for analysis in this study. The relationship between the SEP events and solar activities in four enegy channels were discussed, especially for the physical parameters in the flux ascending phase of SEP event and the heliographic longitude of the source active region. The CMEs and solar flares are also investigated in the ascending phase of the SEP flux profile.Our main results are as follows:First, the source regions of the large SEP events mainly distributed in the western hemisphere, particularly within the longitude range from E40degrees to W40degrees relative to the Earth-well-connected magnetic footpoint.Second, in the presence of fast solar wind, the ascending times in low-energy channel have a good correlation with the relative longitudes by quadratic function, where the closer the source region of the SEP event near the magnetic footpoint, the shorter the ascending time is. However, the relationship between the ascending time and the relative longitude is unclear in the slow solar wind.Third, the ascending time in high-energy channel of the SEP events are dependent on the relative longitude strongly when the solar flare class is high. From the statistical results, we found that the flare acceleration process plays an important role in the ascending phase of SEP events.Finally, the correlation between the ascending times of the SEP events associated with full halo CMEs and the source region longitudes is not outstanding. However, the SEP events associated with partial halo CMEs have a well-fitting quadrati ccurve. The analytical results show that the speed of CMEs correlates with the peak flux intensity of the SEP events, compared to the ascending peak flux intensity, which implies that the CME-driven shock acceleration process plays an important role in the main period of the SEP event.In conclusion, the study in this thesis shows that flare acceleration process mainly reacts on the gradual SEP events merely in ascending phase, especially in those SEP events associated with partial halo CMEs. The peak flux intensity of SEP event is determined by the associated CME, while the ascending peak flux intensity is determined by the associated solar flare.