Mulay, S. M. and Fletcher, L. (2021) Evidence of chromospheric molecular hydrogen emission in a solar flare observed by the IRIS satellite. Monthly Notices of the Royal Astronomical Society, 504(2), pp. 2842-2852. (doi: 10.1093/mnras/stab367)
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Abstract
We have carried out the first comprehensive investigation of enhanced line emission from molecular hydrogen, H2 at 1333.79 Å, observed at flare ribbons in SOL2014-04-18T13:03. The cool H2 emission is known to be fluorescently excited by Si IV 1402.77 Å UV radiation and provides a unique view of the temperature minimum region (TMR). Strong H2 emission was observed when the Si IV 1402.77 Å emission was bright during the flare impulsive phase and gradual decay phase, but it dimmed during the GOES peak. H2 line broadening showed non-thermal speeds in the range 7-18 km s−1, possibly corresponding to turbulent plasma flows. Small red (blue) shifts, up to 1.8 (4.9) km s−1 were measured. The intensity ratio of Si IV 1393.76 Å and Si IV 1402.77 Å confirmed that plasma was optically thin to Si IV (where the ratio = 2) during the impulsive phase of the flare in locations where strong H2 emission was observed. In contrast, the ratio differs from optically thin value of 2 in parts of ribbons, indicating a role for opacity effects. A strong spatial and temporal correlation between H2 and Si IV emission was evident supporting the notion that fluorescent excitation is responsible.
Item Type: | Articles |
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Status: | Published |
Refereed: | Yes |
Glasgow Author(s) Enlighten ID: | Fletcher, Professor Lyndsay and Mulay, Dr Sargam |
Authors: | Mulay, S. M., and Fletcher, L. |
College/School: | College of Science and Engineering > School of Physics and Astronomy |
Journal Name: | Monthly Notices of the Royal Astronomical Society |
Publisher: | Oxford University Press |
ISSN: | 0035-8711 |
ISSN (Online): | 1365-2966 |
Published Online: | 12 February 2021 |
Copyright Holders: | Copyright © 2021 The Authors |
First Published: | First published in Monthly Notices of the Royal Astronomical Society 504(2): 2842-2852 |
Publisher Policy: | Reproduced in accordance with the publisher copyright policy |
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