Suppression of Hydrogen Emission in a White-light Solar Flare [article]

Ondřej Procházka, Ryan Milligan, Joel Allred, Adam Kowalski, Mihalis Mathioudakis
2016 unpublished
We present an analysis of an X-class flare that occurred on 11 June 2014 in active region NOAA 12087 using a newly developed high cadence Image Selector operated by Astronomical Institute in Ondrejov, Czech Republic. This instrument provides spectra in the 350 -440 nm wavelength range, which covers the higher order Balmer lines as well as the Balmer jump at 364 nm. However, no detectable increase in these emissions were detected during the flare, and support observations from SDO/EVE MEGS-B
more » ... SDO/EVE MEGS-B also show that the Lyman line series and recombination continuum were also suppressed, particularly when compared to an M-class flare that occurred an hour earlier, and two other X-class flares on the preceding day. The X-class flare under investigation also showed strong white light emission in SDO/HMI data, as well as an extremely hard electron spectrum (δ ≈ 3.6), and γ-ray emission, from RHESSI data. This unique combination of datasets allows us to conclude that the white light emission from this flare corresponds to a black body heated by high-energy electrons (and/or ions), as opposed to optical chromospheric emission from hydrogen.
doi:10.13140/rg.2.1.3294.8722 fatcat:lf5ddjeg5jhjrc5ffjnul4n254