Bright Ray-like Features in the Aftermath of CMEs: White Light vs UV Spectra

TL;DR

This study compares white light and UV spectral observations of rays in CME aftermaths, revealing diverse temperature structures and origins, including hot current sheets and cool prominence material, with implications for understanding magnetic reconnection.

Contribution

It provides a detailed analysis of the temperature and composition of CME-associated rays in white light and UV spectra, highlighting their varied nature and origins, which was not comprehensively characterized before.

Findings

18% of white light rays are consistent with hot current sheets

23% of UV rays are cool prominence material

Many rays contain both hot and cool components, often offset spatially.

Abstract

Current sheets are important signatures of magnetic reconnection in the eruption of confined solar magnetic structures. Models of Coronal Mass Ejections (CMEs) involve formation of a current sheet connecting the ejected flux rope with the post eruption magnetic loops. Current sheets have been identified in white light images of CMEs as narrow rays trailing the outward moving CME core, and in ultraviolet spectra as narrow bright features emitting the Fe XVIII line. In this work samples of rays detected in white light images or in ultraviolet spectra have been analyzed. Temperatures, widths, and line intensities of the rays have been measured, and their correlation to the CME properties has been studied. The samples show a wide range of temperatures with hot, coronal and cool rays. In some cases, the UV spectra support the identification of rays as current sheets, but they show that some white light rays are cool material from the CME core. In many cases, both hot and cool material are present, but offset from each other along the UltraViolet Coronagraph Spectrometer (UVCS) slit. We find that about 18% of the white light rays show very hot gas consistent with the current sheet interpretation, while about 23% show cold gas that we attribute to cool prominence material draining back from the CME core. The remaining events have ordinary coronal temperatures, perhaps because they have relaxed back to a quiescent state.