Physical properties of White-Light Sources in the 2011 Feb 15 Solar Flare

Kerr, G.S. and Fletcher, L. (2014) Physical properties of White-Light Sources in the 2011 Feb 15 Solar Flare. Astrophysical Journal, 783(2), Art. 98. (doi:10.1088/0004-637X/783/2/98)

Kerr, G.S. and Fletcher, L. (2014) Physical properties of White-Light Sources in the 2011 Feb 15 Solar Flare. Astrophysical Journal, 783(2), Art. 98. (doi:10.1088/0004-637X/783/2/98)

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Abstract

White light flares (WLFs) are observational rarities, making them understudied events. However, optical emission is a significant contribution to flare energy budgets and the emission mechanisms responsible could have important implications for flare models. Using Hinode SOT optical continuum data taken in broadband red, green and blue filters, we investigate white-light emission from the X2.2 flare SOL2011-02-15T01:56:00. We develop a technique to robustly identify enhanced flare pixels and, using a knowledge of the RGB filter transmissions, determined the source color temperature and effective temperature. We investigated two idealized models of WL emission - an optically thick photospheric source, and an optically thin chromospheric slab. Under the optically thick assumption, the color temperature and effective temperature of flare sources in sunspot umbra and penumbra were determined as a function of time and position. Values in the range of 5000-6000K were found, corresponding to a blackbody temperature increase of a few hundred kelvin. The power emitted in the optical was estimated at ∼1026ergs/s. In some of the white-light sources the color and blackbody temperatures are the same within uncertainties, consistent with a blackbody emitter. In other regions this is not the case, suggesting that some other continuum emission process is contributing. An optically thin slab model producing hydrogen recombination radiation is also discussed as a potential source of WL emission; it requires temperatures in the range 5,500 - 25,000K, and total energies of ∼1027 ergs/s

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Kerr, Graham and Fletcher, Professor Lyndsay
Authors: Kerr, G.S., and Fletcher, L.
Subjects:Q Science > QB Astronomy
Q Science > QC Physics
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Group:Astronomy and Astrophysics
Journal Name:Astrophysical Journal
Journal Abbr.:Ap.J.
Publisher:Institute of Physics
ISSN:0004-637X
ISSN (Online):1538-4357
Copyright Holders:Copyright © 2014 The American Astronomical Society
First Published:First published in Astrophysical Journal 783(2):98
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
542081Rolling Programme in Solar and Plasma AstrophysicsLyndsay FletcherScience & Technologies Facilities Council (STFC)ST/I001808/1P&A - PHYSICS & ASTRONOMY
537641High Energy Solar Physics Data in Europe HESPELyndsay FletcherEuropean Commission (EC)UNSPECIFIEDP&A - PHYSICS & ASTRONOMY