Non-thermal line broadening due to braiding-induced turbulence in solar coronal loops

D. I. Pontin (Lead / Corresponding author), H. Peter, L. P. Chitta

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Abstract

Aims. Emission line profiles from solar coronal loops exhibit properties that are unexplained by current models. We investigate the non-thermal broadening associated with plasma heating in coronal loops that is induced by magnetic field line braiding. Methods. We describe the coronal loop by a 3D magnetohydrodynamic model of the turbulent decay of an initially-braided magnetic field. From this, we synthesised the Fe » XII line at 193 Å that forms around 1.5 MK. Results. The key features of current observations of extreme ultraviolet (UV) lines from the corona are reproduced in the synthesised spectra: (i) Typical non-thermal widths range from 15 to 20 km s-1. (ii) The widths are approximately independent of the size of the field of view. (iii) There is a correlation between the line intensity and non-thermal broadening. (iv) Spectra are found to be non-Gaussian, with enhanced power in the wings of the order of 10-20%. Conclusions. Our model provides an explanation that self-consistently connects the heating process to the observed non-thermal line broadening. The non-Gaussian nature of the spectra is a consequence of the non-Gaussian nature of the underlying velocity fluctuations, which is interpreted as a signature of intermittency in the turbulence.

Original languageEnglish
Article numberA21
Pages (from-to)1-9
Number of pages9
JournalAstronomy and Astrophysics
Volume639
Early online date2 Jun 2020
DOIs
Publication statusPublished - Jul 2020

Keywords

  • Sun:corona
  • line:profiles
  • magnetohydrodynamics
  • turbulence
  • magnetic reconnection
  • Magnetic reconnection
  • Turbulence
  • Sun: corona
  • Magnetohydrodynamics (MHD)
  • Line: profiles

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