Temperature Dependence of the Flare Fluence Scaling Exponent

Abstract : Solar flares result in an increase of the solar irradiance at all wavelengths. While the distribution of the flare fluence observed in coronal emission has been widely studied and found to scale as , with slightly below 2, the distribution of the flare fluence in chromospheric lines is poorly known. We used the solar irradiance measurements observed by the SDO/EVE instrument at a 10 s cadence to investigate the dependency of the scaling exponent on the formation region of the lines (or temperature). We analyzed all flares above the C1 level since the start of the EVE observations (May 2010) to determine the flare fluence distribution in 16 lines covering a wide range of temperatures, several of which were not studied before. Our results show a weak downward trend with temperature of the scaling exponent of the PDF that reaches from above 2 at lower temperature (a few ) to for hot coronal emission (several ). However, because colder lines also have fainter contrast, we cannot exclude that this behavior is caused by including more noise for smaller flares for these lines. We discuss the method and its limitations and tentatively associate this possible trend with the different mechanisms responsible for the heating of the chromosphere and corona during flares.
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Submitted on : Wednesday, January 13, 2016 - 10:30:12 AM
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Mathieu Kretzschmar. Temperature Dependence of the Flare Fluence Scaling Exponent. Solar Physics, Springer Verlag, 2015, 290 (12), pp. 3593-3609. ⟨10.1007/s11207-015-0783-z⟩. ⟨insu-01255042⟩



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