Formation of the thermal infrared continuum in solar flares

Simões, P. J.A. , Kerr, G. S., Fletcher, L. , Hudson, H. S. , Giménez de Castro, C. G. and Penn, M. (2017) Formation of the thermal infrared continuum in solar flares. Astronomy and Astrophysics, 605, A125. (doi: 10.1051/0004-6361/201730856)

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Aims. Observations of the Sun with the Atacama Large Millimeter Array have now started, and the thermal infrared will regularly be accessible from the NSF’s Daniel K. Inouye Solar Telescope. Motivated by the prospect of these new data, and by recent flare observations in the mid infrared, we set out here to model and understand the source of the infrared continuum in flares, and to explore its diagnostic capability for the physical conditions in the flare atmosphere. Methods. We use the one-dimensional (1D) radiation hydrodynamics code RADYN to calculate mid-infrared continuum emission from model atmospheres undergoing sudden deposition of energy by non-thermal electrons. Results. We identify and characterise the main continuum thermal emission processes relevant to flare intensity enhancement in the mid- to far-infrared (2–200 μm) spectral range as free-free emission on neutrals and ions. We find that the infrared intensity evolution tracks the energy input to within a second, albeit with a lingering intensity enhancement, and provides a very direct indication of the evolution of the atmospheric ionisation. The prediction of highly impulsive emission means that, on these timescales, the atmospheric hydrodynamics need not be considered in analysing the mid-IR signatures.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Simoes, Dr Paulo and Fletcher, Professor Lyndsay and Hudson, Dr Hugh and Kerr, Graham
Authors: Simões, P. J.A., Kerr, G. S., Fletcher, L., Hudson, H. S., Giménez de Castro, C. G., and Penn, M.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN (Online):1432-0746
Published Online:20 September 2017
Copyright Holders:Copyright © 2017 ESO
First Published:First published in Astronomy and Astrophysics 605:A125
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
595181Chromospheric Flares: Observations, Models and Archives (CHROMA)Lyndsay FletcherEuropean Commission (EC)606862P&A - PHYSICS & ASTRONOMY
631581Consolidated grant in solar and astrophysical plasmasLyndsay FletcherScience & Technology Facilities Council (STFC)ST/L000741/1S&E P&A - PHYSICS & ASTRONOMY