The Spatial and Temporal Variations of Turbulence in a Solar Flare

Stores, Morgan, Jeffrey, Natasha L. S. and Kontar, Eduard (2021) The Spatial and Temporal Variations of Turbulence in a Solar Flare. The Astrophysical Journal. ISSN 0004-637X (In Press)

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Abstract

Magnetohydrodynamic (MHD) plasma turbulence is believed to play a vital role in the production of energetic electrons during solar flares and the non-thermal 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 Hinode/EIS. Maps of non-thermal 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 non-thermal velocity decreases as the flare evolves and during/after the X-ray peak shows a clear spatial variation decreasing linearly from the loop apex towards the ribbon. For the cooler ion (Fe xvi), the non-thermal 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: Article
Additional Information: NLSJ 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. MS gratefully acknowledges the financial support from the Northumbria University RDF studentship. The authors acknowledge IDL support provided by STFC. The work is supported by an international team grant “Solar flare acceleration signatures and their connection to solar energetic particles” from the International Space Sciences Institute (ISSI) Bern, Switzerland. Hinode is a Japanese mission developed and launched by ISAS/JAXA, with NAOJ as domestic partner and NASA and UKSA as international partners. It is operated by these agencies in co-operation with ESA and NSC (Norway). CHIANTI is a collaborative project involving George Mason University, the University of Michigan (USA), University of Cambridge (UK) and NASA Goddard Space Flight Center (USA).
Uncontrolled Keywords: Sun: flares, Sun: chromosphere, Sun: corona, Sun: UV radiation, turbulence, techniques: spectroscopic
Subjects: F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: John Coen
Date Deposited: 13 Oct 2021 12:59
Last Modified: 13 Oct 2021 13:03
URI: http://nrl.northumbria.ac.uk/id/eprint/47478

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