Energetic Particles from Quasi-Separatrix Layers and Current Sheets at the Sun

TL;DR

This paper introduces the first global model of energetic particles accelerated at the Sun's quasi-separatrix layers and current sheets, highlighting their role as seed populations enriched in $^3$He and heavy ions, crucial for understanding solar energetic particle events.

Contribution

The study presents a novel global model linking magnetic reconnection at QSLs and current sheets to energetic particle acceleration, emphasizing the composition of seed populations.

Findings

Energetic particles are accelerated from QSLs and current sheets at the Sun.

Seed populations are enriched in $^3$He and heavy ions.

The model supports the role of magnetic reconnection in particle acceleration.

Abstract

Quasi-separatrix layers (QSLs) at the Sun are created from regions where channels of open magnetic flux have footpoints near regions of large-scale closed magnetic flux. These regions are particularly prone to magnetic reconnection at the Sun. In recent simulations of coronal mass ejections (CMEs) with the Magnetohydrodynamic Algorithm outside a Sphere (MAS) model coupled to the Energetic Particle Radiation Environment Module (EPREM) model, common sources of energetic particles were discovered over broad longitudinal distributions in the background solar wind, far from the sites of particle acceleration driven by compressions and shocks in front of CMEs. Further investigation revealed these to be accelerated energetic particles from the QSLs and current sheets. The energy released from magnetic reconnection near the QSL drives reconnection exhausts and field-aligned flows, which in turn accelerate energetic particles. The reconnection process also releases material previously contained within closed magnetic field structures, which are often rich in heavy ions and $^3$He ions, as corroborated by recent PSP observations. Therefore, the seed populations produced by QSLs are expected to be rich in $^3$He and heavy ions. Thus, we present the first global model of energetic particles accelerated from QSLs and above current sheets from the Sun. Our results provide a plausible source for seed populations near the Sun, which likely have $^3$He and heavy ion enhancements. These results aid in the development of predictive solar energetic particle models.