Statistical Analysis of the Relation between Coronal Mass Ejections and Solar Energetic Particles

To improve the forecasting capability of impactful solar energetic particle (SEP) events, the relation between coronal mass ejections (CMEs) and SEP events needs to be better understood. Here we present a statistical study of SEP occurrences and timescales with respect to the CME source locations and speeds, considering all 257 fast (v(CME)>= 900 km s(-1)) and wide (angular width >= 60 degrees) CMEs that occurred between 2006 December and 2017 October. We associate them with SEP events at energies above 10 MeV. Examination of the source region of each CME reveals that CMEs more often accompany a SEP event if they originate from the longitude of E20-W100 relative to the observer. However, an SEP event could still be absent if the CME is <2000 km s(-1). For the associated CME-SEP pairs, we compute three timescales for each of the SEP events, namely the timescale of the onset (TO), the rise time (TR), and the duration (TD). They are correlated with the longitude of the CME source region relative to the footpoint of the Parker spiral (Delta phi) and v(CME). The TO tends to be short for for |Delta Phi| < 60 degrees. This trend is weaker for TR and TD. The SEP timescales are only weakly correlated with v(CME). Positive correlations of both TR and TD with vCME are seen in poorly connected (large |Delta Phi|) events. Additionally, TO appears to be negatively correlated with vCME for events with small |Delta Phi|.