Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare

Abstract

We examine spectropolarimetric data from the CoMP instrument, acquired during the evolution of the September 10th 2017 X8.2 solar flare on the western solar limb. CoMP captured linearly polarized light from two emission lines of Fe XIII at 1074.7 and 1079.8 nm, from 1.03 to 1.5 solar radii. We focus here on the hot plasma-sheet lying above the bright flare loops and beneath the ejected CME. The polarization has a striking and coherent spatial structure, with unexpectedly small polarization aligned with the plasma-sheet. By elimination, we find that small-scale magnetic field structure is needed to cause such significant depolarization, and suggest that plasmoid formation during reconnection (associated with the tearing mode instability) creates magnetic structure on scales below instrument resolution of 6 Mm. We conclude that polarization measurements with new coronagraphs, such as the upcoming DKIST, will further enhance our understanding of magnetic reconnection and development of turbulence in the solar corona.

9 pages, 4 figures; accepted for publication to ApJ Letters

References in corpus (4)

• Instability of current sheets and formation of plasmoid chains
• Multi-scale Gaussian normalization for solar image processing
• Mapping the magnetic field of flare coronal loops
• Magnetic nulls and super-radial expansion in the solar corona

Cited by in corpus (4)

• Magnetic Reconnection During the Post-Impulsive Phase of a Long-Duration Solar Flare: Bi-Directional Outflows as a Cause of Microwave and X-ray Bursts
• Microwave Spectral Imaging of an Erupting Magnetic Flux Rope: Implications for the Standard Solar Flare Model in Three Dimensions
• Electron Densities in the Solar Corona Measured Simultaneously in the Extreme-Ultraviolet and Infra-Red
• Observations of Thomson scattering from a loop-prominence system