Seed population in large Solar Energetic Particle events and the twin-CME scenario

Abstract

It has been recently suggested that large solar energetic particle (SEP) events are often caused by twin CMEs. In the twin-CME scenario, the preceding CME is to provide both an enhanced turbulence level and enhanced seed population at the main CME-driven shock. In this work, we study the effect of the preceding CMEs on the seed population. We examine event-integrated abundance of iron to oxygen ratio (Fe/O) at energies above 25 MeV/nuc for large SEP events in solar cycle 23. We find that the Fe/O ratio (normalized to the reference coronal value of $0.134$) $\le 2.0$ for almost all single-CME events and these events tend to have smaller peak intensities. In comparison, the Fe/O ratio of twin-CME events scatters in a larger range, reaching as high as $8$, suggesting the presence of flare material from perhaps preceding flares. For extremely large SEP events with peak intensity above $1000$ pfu, the Fe/O drop below $2$, indicating that in these extreme events the seed particles are dominated by coronal material than flare material. The Fe/O ratios of Ground level enhancement (GLE) events, all being twin-CME events, scatter in a broad range. For a given Fe/O ratio, GLE events tend to have larger peak intensities than non-GLE events. Using velocity dispersion analysis (VDA), we find that GLE events have lower solar particle release (SPR) heights than non-GLE events, \red{agreeing with earlier results by Reames 2009b.

References in corpus (3)

• Element Abundances in Solar Energetic Particles and the Solar Corona
• Abundance Enhancements in Impulsive Solar Energetic-Particle Events with Associated Coronal Mass Ejections
• Temperature of the Source Plasma for Impulsive Solar Energetic Particles

Cited by in corpus (7)

• Plasma compression in magnetic reconnection regions in the solar corona
• Large solar energetic particle event that occurred on 2012 March 7 and its VDA analysis
• Is the enhancement of type II radio bursts during CME interactions related to the associated solar energetic particle event?
• Tests for coronal electron temperature signatures in suprathermal electron populations at 1 AU
• Physics-Based Simulation of the 2013 April 11 Solar Energetic Particle Event
• Statistical characteristics on SEPs, radio-loud CMEs, low frequency type II and type III radio bursts associated with impulsive and gradual flares
• Successive Coronal Mass Ejections Associated with Weak Solar Energetic Particle Events