Solar Physics

, Volume 290, Issue 12, pp 3593–3609 | Cite as

Temperature Dependence of the Flare Fluence Scaling Exponent

  • M. KretzschmarEmail author
Solar and Stellar Flares


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 \(f(E)\sim E^{-\alpha}\), with \(\alpha\) 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 \(10^{4}~\mbox{K}\)) to \({\sim\,}1.8\) for hot coronal emission (several \(10^{6}~\mbox{K}\)). 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.


Flares Solar irradiance Heating, in flares 



The author acknowledges the SDO/EVE and GOES teams (in particular Janet Machol for the Ly-\(\alpha\) data) for providing the data, as well as the organizers and attendants of the “Solar and Stellar Flares” meeting in Prague, 2014, for a very successful and interesting meeting. The author also acknowledges the referee for comments that significantly helped to improve the article. Part of this research has been funded by the European Community’s Seventh Framework Programme (FP7 2012) under grant agreement no 313188 (SOLID project).


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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  1. 1.LPC2E, UMR 7328 CNRSUniversity of OrléansOrléansFrance

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