Hα and Hβ Emission in a C3.3 Solar Flare: Comparison between Observations and Simulations
Abstract
The hydrogen Balmer series is a basic radiative loss channel from the flaring solar chromosphere. We report here on the analysis of an extremely rare set of simultaneous observations of a solar flare in the {{H}}α and {{H}}β lines, at high spatial and temporal resolutions, that were acquired at the Dunn Solar Telescope. Images of the C3.3 flare (SOL2014-04-22T15:22) made at various wavelengths along the {{H}}α line profile by the Interferometric Bidimensional Spectrometer (IBIS) and in the {{H}}β with the Rapid Oscillations in the Solar Atmosphere (ROSA) broadband imager are analyzed to obtain the intensity evolution. The {{H}}α and {{H}}β intensity excesses in three identified flare footpoints are well-correlated in time. We examine the ratio of {{H}}α to {{H}}β flare excess, which was proposed by previous authors as a possible diagnostic of the level of electron-beam energy input. In the stronger footpoints, the typical value of the the {{H}}α /H β intensity ratio observed is ∼0.4-0.5, in broad agreement with values obtained from a RADYN non-LTE simulation driven by an electron beam with parameters constrained (as far as possible) by observation. The weaker footpoint has a larger {{H}}α /H β ratio, again consistent with a RADYN simulation, but with a smaller energy flux. The {{H}}α line profiles observed have a less prominent central reversal than is predicted by the RADYN results, but can be brought into agreement if the {{H}}α -emitting material has a filling factor of around 0.2-0.3.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2017
- DOI:
- 10.3847/1538-4357/aa9187
- arXiv:
- arXiv:1710.04067
- Bibcode:
- 2017ApJ...850...36C
- Keywords:
-
- Sun: activity;
- Sun: chromosphere;
- Sun: flares;
- Sun: photosphere;
- techniques: high angular resolution;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 14 pages, 17 figures