The spatial and temporal variations of turbulence in a solar flare

Stores, M., Jeffrey, N. L.S. and Kontar, E. P. (2021) The spatial and temporal variations of turbulence in a solar flare. Astrophysical Journal, 923(1), 40. (doi: 10.3847/1538-4357/ac2c65)

Abstract

Magnetohydrodynamic plasma turbulence is believed to play a vital role in the production of energetic electrons during solar flares, and the nonthermal broadening of spectral lines is a key sign of this turbulence. Here, we determine how flare turbulence evolves in time and space using spectral profiles of Fe xxiv, Fe xxiii, and Fe xvi, observed by the Hinode/EUV Imaging Spectrometer. Maps of nonthermal velocity are created for times covering the X-ray rise, peak, and decay. For the first time, the creation of kinetic energy density maps reveal where energy is available for energization, suggesting that similar levels of energy may be available to heat and/or accelerate electrons in large regions of the flare. We find that turbulence is distributed throughout the entire flare, often greatest in the coronal loop tops, and decaying at different rates at different locations. For hotter ions (Fe xxiv and Fe xxiii), the nonthermal velocity decreases as the flare evolves and during/after the X-ray peak shows a clear spatial variation decreasing linearly from the loop apex toward the ribbon. For the cooler ion (Fe xvi), the nonthermal velocity remains relativity constant throughout the flare, but steeply increases in one region corresponding to the southern ribbon, peaking just prior to the peak in hard X-rays before declining. The results suggest turbulence has a more complex temporal and spatial structure than previously assumed, while newly introduced turbulent kinetic energy maps show the availability of the energy and identify important spatial inhomogeneities in the macroscopic plasma motions leading to turbulence.

• Item Type: Articles
• Additional Information: N.L.S.J. gratefully acknowledges the current financial support from the Science and Technology Facilities Council (STFC) Grant ST/V000764/1 and previous support from STFC Grant ST/P000533/1. M.S. gratefully acknowledges the financial support from the Northumbria University RDF studentship.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Jeffrey, Dr Natasha and Kontar, Professor Eduard
• Authors: Stores, M., Jeffrey, N. L.S., and Kontar, E. P.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Astrophysical Journal
• Publisher: The American Astronomical Society
• ISSN: 1538-4357
• ISSN (Online): 1538-4357
• Copyright Holders: Copyright © 2021. The Author(s)
• First Published: First published in Astrophysical Journal 923(1):40
• Publisher Policy: Reproduced under a Creative Commons Licence

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
173869		Consolidated Grant in Solar Physics	Lyndsay Fletcher	Science and Technology Facilities Council (STFC)	ST/P000533/1	P&S - Physics & Astronomy