First Detection of Solar Flare Emission in Mid-ultraviolet Balmer Continuum

0497530 - ASÚ 2019 RIV US eng J - Journal Article
Dominique, M. - Zhukov, A. N. - Heinzel, Petr - Dammasch, I.F. - Wauters, L. - Dona, L. - Shestov, S. V. - Kretzschmar, M. - Machol, J. - Lapenta, G. - Schmutz, W.
First Detection of Solar Flare Emission in Mid-ultraviolet Balmer Continuum.
Astrophysical Journal Letters. Roč. 867, č. 2 (2018), č. článku L4. ISSN 2041-8205. E-ISSN 2041-8213
R&D Projects: GA ČR(CZ) GA16-18495S
Institutional support: RVO:67985815
Keywords : Sun * chromosphere * flares
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 8.374, year: 2018

We present the first detection of solar flare emission at mid-ultraviolet wavelengths around 2000 angstrom by the channel 2 of the Large-Yield RAdiometer (LYRA) on board the PRoject for OnBoard Autonomy 2 mission. The flare (SOL20170906) was also observed in the channel 1 of LYRA centered at the H I Ly alpha line at 1216 angstrom, showing a clear non-thermal profile in both channels. The flare radiation in channel 2 is consistent with the hydrogen Balmer continuum emission produced by an optically thin chromospheric slab heated up to 10,000 K. Simultaneous observations in channels 1 and 2 allow the separation of the line emission (primarily from the Lya line) from the Balmer continuum emission. Together with the recent detection of the Balmer continuum emission in the near-ultraviolet by the Interface Region Imaging Spectrometer, the LYRA observations strengthen the interpretation of broadband flare emission as the hydrogen recombination continua originating in the chromosphere.
Permanent Link: http://hdl.handle.net/11104/0290090