Observations of enhanced extreme ultraviolet continua during an x-class solar flare usingsdo/eve

Milligan, R.O., Chamberlin, P.C., Hudson, H.S., Woods, T.N., Mathioudakis, M., Fletcher, L. , Kowalski, A.F. and Keenan, F.P. (2012) Observations of enhanced extreme ultraviolet continua during an x-class solar flare usingsdo/eve. Astrophysical Journal Letters, 748(1), L14. (doi:10.1088/2041-8205/748/1/L14)

Milligan, R.O., Chamberlin, P.C., Hudson, H.S., Woods, T.N., Mathioudakis, M., Fletcher, L. , Kowalski, A.F. and Keenan, F.P. (2012) Observations of enhanced extreme ultraviolet continua during an x-class solar flare usingsdo/eve. Astrophysical Journal Letters, 748(1), L14. (doi:10.1088/2041-8205/748/1/L14)

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Abstract

Observations of extreme ultraviolet (EUV) emission from an X-class solar flare that occurred on 2011 February 15 at 01:44 UT are presented, obtained using the EUV Variability Experiment (EVE) on board the Solar Dynamics Observatory. The complete EVE spectral range covers the free-bound continua of H I (Lyman continuum), He I, and He II, with recombination edges at 91.2, 50.4, and 22.8 nm, respectively. By fitting the wavelength ranges blueward of each recombination edge with an exponential function, light curves of each of the integrated continua were generated over the course of the flare, as was emission from the free-free continuum (6.5-37 nm). The He II 30.4 nm and Lyα 121.6 nm lines, and soft X-ray (SXR; 0.1-0.8 nm) emission from GOES are also included for comparison. Each free-bound continuum was found to have a rapid rise phase at the flare onset similar to that seen in the 25-50 keV light curves from RHESSI, suggesting that they were formed by recombination with free electrons in the chromosphere. However, the free-free emission exhibited a slower rise phase seen also in the SXR emission from GOES, implying a predominantly coronal origin. By integrating over the entire flare the total energy emitted via each process was determined. We find that the flare energy in the EVE spectral range amounts to at most a few percent of the total flare energy, but EVE gives us a first comprehensive look at these diagnostically important continuum components.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Fletcher, Professor Lyndsay
Authors: Milligan, R.O., Chamberlin, P.C., Hudson, H.S., Woods, T.N., Mathioudakis, M., Fletcher, L., Kowalski, A.F., and Keenan, F.P.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal Letters
ISSN:2041-8205
ISSN (Online):2041-8213

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