OBSERVATIONS OF ENHANCED EXTREME ULTRAVIOLET CONTINUA DURING AN X-CLASS SOLAR FLARE USING SDO/EVE

Journal Article · Tue Mar 20 04:00:00 EDT 2012 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/748/1/L14· OSTI ID:22047948

Milligan, Ryan O; Mathioudakis, Mihalis; Keenan, Francis P ^[1]; Chamberlin, Phillip C ^[2]; Hudson, Hugh S ^[3]; Woods, Thomas N ^[4]; Fletcher, Lyndsay ^[5]

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1. Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN (United Kingdom)
2. Solar Physics Laboratory (Code 671), Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
3. Space Sciences Laboratory, UC Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450 (United States)
4. Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States)
5. School of Physics and Astronomy, SUPA, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

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 Ly{alpha} 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.

• OSTI ID: 22047948
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 748; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
CHROMOSPHERE
COMPARATIVE EVALUATIONS
ELECTRONS
EXTREME ULTRAVIOLET RADIATION
GAMMA ASTRONOMY
GAMMA RADIATION
KEV RANGE
LYMAN LINES
RECOMBINATION
SOFT X RADIATION
SOLAR FLARES
SUN
VISIBLE RADIATION