Statistical Evidence for Contributions of Flares and Coronal Mass Ejections to Major Solar Energetic Particle Events
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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.
KeywordsCoronal mass ejections Energetic particles, acceleration Energetic particles, propagation Flares, energetic particles
The authors acknowledge D. Boscher (ONERA Toulouse) for making the IPODE database of GOES particle measurements available to us. We acknowledge the generous supply of data from the ACE/EPAM particle instrument, the GOES particle and soft X-ray detectors, the Wind/WAVES radio spectrograph, the RSTN and NoRP radio instruments, and the Radio Monitoring web site http://secchirh.obspm.fr/index.php at Paris Observatory. Extensive use was made of the CME catalogue generated and maintained at the CDAW Data Center by NASA and The Catholic University of America in cooperation with the Naval Research Laboratory. SOHO is a project of international cooperation between ESA and NASA. The work presented here benefitted from partial financial support and from scientific cooperation within the SEPServer (Grant Agreement No. 262773) and HESPE (Grant Agreement No. 263086) projects of the 7th Framework programme of the European Union. This research was carried out within a collaboration between Egypt and France funded through the IMHOTEP programme (contracts 23190YB and 27471UK). We are grateful to the Egyptian coordinator, M. Shaltout, for his support. We also acknowledge support by the Centre National d’Etudes Spatiales (CNES). The referee is thanked for the careful reading of the manuscript and helpful comments.
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