Suppression of hydrogen emission in an X-class white-light solar flare

Procházka, O., Milligan, R. O. , Allred, J. C., Kowalski, A. F., Kotrč, P. and Mathioudakis, M. (2017) Suppression of hydrogen emission in an X-class white-light solar flare. Astrophysical Journal, 837(1), 46. (doi: 10.3847/1538-4357/aa5da8)

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Abstract

We present unique NUV observations of a well-observed X-class flare from NOAA 12087 obtained at the Ondřejov Observatory. The flare shows a strong white-light continuum but no detectable emission in the higher Balmer and Lyman lines. Reuven Ramaty High-Energy Solar Spectroscopic Imager and Fermi observations indicate an extremely hard X-ray spectrum and γ-ray emission. We use the RADYN radiative hydrodynamic code to perform two types of simulations: one where an energy of 3 × 1011 erg cm−2 s−1 is deposited by an electron beam with a spectral index of ≈3, and a second where the same energy is applied directly to the photosphere. The combination of observations and simulations allows us to conclude that the white-light emission and the suppression or complete lack of hydrogen emission lines is best explained by a model where the dominant energy deposition layer is located in the lower layers of the solar atmosphere, rather than the chromosphere.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Milligan, Dr Ryan
Authors: Procházka, O., Milligan, R. O., Allred, J. C., Kowalski, A. F., Kotrč, P., and Mathioudakis, M.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
Publisher:IOP Publishing
ISSN:1538-4357
ISSN (Online):1538-4357
Copyright Holders:Copyright © 2017 The American Astronomical Society
First Published:First published in Astrophysical Journal 837(1):46
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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