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

TL;DR

This study statistically analyzes the relationship between fast, wide CMEs and solar energetic particle events, revealing how CME source location and speed influence SEP occurrence and timing characteristics.

Contribution

It provides new insights into how CME source longitude and speed affect SEP event timing and occurrence, enhancing forecasting models.

Findings

SEP events are more likely when CMEs originate from certain longitudes.

CME speed weakly correlates with SEP timescales.

SEP onset times are shorter for certain source locations.

Abstract

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 ($v_{CME}$ $\ge$ 900 km/s) and wide (angular width $\ge$ 60$^{\circ}$) CMEs that occurred between December 2006 and October 2017. 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, a SEP event could still be absent if the CME is $<$ 2000 km/s. For the associated CME-SEP pairs, we compute three timescales for each of the SEP events, following Kahler (2005, 2013); 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 $|\Delta\Phi|$ $<$ 60$^{\circ}$ . 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 $v_{CME}$ are seen in poorly connected (large $|\Delta\Phi|$) events. Additionally, TO appears to be negatively correlated with $v_{CME}$ for events with small $|\Delta\Phi|$.