The Sun as a star: observations of white-light flares
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Publication:4905724
DOI10.1051/0004-6361/201015930zbMATH Open1260.85058arXiv1103.3125OpenAlexW3098990878WikidataQ68998758 ScholiaQ68998758MaRDI QIDQ4905724
Author name not available (Why is that?)
Publication date: 20 February 2013
Published in: (Search for Journal in Brave)
Abstract: Solar flares radiates energy at all wavelengths, but the spectral distribution of this energy is still poorly known. White-light continuum emission is sometimes observed and the flares are then termed "white-light flares" (WLF). In this paper, we investigate if all flares are white-light flares and how is the radiated energy spectrally distributed. We perform a superposed epoch analysis of spectral and total irradiance measurements obtained since 1996 by the SOHO and GOES spacecrafts at various wavelength, from Soft X-ray to the visible domain. The long-term record of solar irradiance and excellent duty cycle of the measurements allow us to detect a signal in visible irradiance even for moderate (C-class) flares, mainly during the impulsive phase. We identify this signal as continuum emission emitted by white-light flares, and find that it is consistent with a blackbody emission at ~9000K. We estimate for several sets of flares the contribution of the WL continuum and find it to be of ~70% of the total radiated energy. We re-analyse the X17 flare that occurred on 28 October 2003 and find similar results. This paper brings evidence that all flares are white-light flares and that the white-light continuum is the main contributor to the total radiated energy; this continuum is consistent with blackbody spectrum at ~9000K. These observational results are important in order to understand the physical mechanisms during flares and open the way to a possible contribution of flares to TSI variations.
Full work available at URL: https://arxiv.org/abs/1103.3125
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