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Title: Suppression of Hydrogen Emission in an X-class White-light Solar Flare

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 × 10{sup 11} erg cm{sup −2} s{sup −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.

Authors:
; ;  [1];  [2];  [3];  [4]
  1. Astrophysics Research Centre, Queen’s University Belfast, Northern Ireland (United Kingdom)
  2. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  3. Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, 2000 Colorado Avenue, Boulder, CO 80305 (United States)
  4. Astronomical Institute, The Czech Academy of Sciences, 25165 Ondřejov (Czech Republic)
Publication Date:
OSTI Identifier:
22661330
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 837; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHROMOSPHERE; ELECTRON BEAMS; EMISSION; ENERGY ABSORPTION; ENERGY LOSSES; GAMMA RADIATION; HARD X RADIATION; HYDRODYNAMICS; HYDROGEN; LAYERS; LYMAN LINES; PHOTOSPHERE; SIMULATION; SOLAR FLARES; SUN; VISIBLE RADIATION; X-RAY SPECTRA

Citation Formats

Procházka, Ondrej, Milligan, Ryan O., Mathioudakis, Mihalis, Allred, Joel C., Kowalski, Adam F., and Kotrč, Pavel, E-mail: oprochazka01@qub.ac.uk. Suppression of Hydrogen Emission in an X-class White-light Solar Flare. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA5DA8.
Procházka, Ondrej, Milligan, Ryan O., Mathioudakis, Mihalis, Allred, Joel C., Kowalski, Adam F., & Kotrč, Pavel, E-mail: oprochazka01@qub.ac.uk. Suppression of Hydrogen Emission in an X-class White-light Solar Flare. United States. doi:10.3847/1538-4357/AA5DA8.
Procházka, Ondrej, Milligan, Ryan O., Mathioudakis, Mihalis, Allred, Joel C., Kowalski, Adam F., and Kotrč, Pavel, E-mail: oprochazka01@qub.ac.uk. Wed . "Suppression of Hydrogen Emission in an X-class White-light Solar Flare". United States. doi:10.3847/1538-4357/AA5DA8.
@article{osti_22661330,
title = {Suppression of Hydrogen Emission in an X-class White-light Solar Flare},
author = {Procházka, Ondrej and Milligan, Ryan O. and Mathioudakis, Mihalis and Allred, Joel C. and Kowalski, Adam F. and Kotrč, Pavel, E-mail: oprochazka01@qub.ac.uk},
abstractNote = {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 × 10{sup 11} erg cm{sup −2} s{sup −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.},
doi = {10.3847/1538-4357/AA5DA8},
journal = {Astrophysical Journal},
number = 1,
volume = 837,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}
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