Frequency rising sub-THz emission from solar flare ribbons |
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Galina Motorina Submitted: 2018-10-11 01:09
Observations of solar flares at sub-THz frequencies (mm and sub-mm wavelengths) over the last two decades often show a spectral component rising with frequency. Unlike a typical gyrosynchrotron spectrum decreasing with frequency, or a weak thermal component from hot coronal plasma, the observations can demonstrate a high flux level (up to ~104 s.f.u. at 0.4 THz) and fast variability on sub-second time scales. Although, many models has been put forward to explain the puzzling observations, none of them have clear observational support. Here we propose a scenario to explain the intriguing sub-THz observations. We show that the model, based on free-free emission from the plasma of flare ribbons at temperatures 104-106 K, is consistent with all existing observations of frequency-rising sub-THz flare emission. The model provides a temperature diagnostic of the flaring chromosphere and suggests fast heating and cooling of the dense transition region plasma.
Authors: Kontar, E. P.; Motorina, G. G.; Jeffrey, N. L. S.; Tsap, Y. T.; Fleishman, G. D.; Stepanov, A. V.
Projects: None
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Publication Status: Astronomy and Astrophysics, accepted
Last Modified: 2018-10-15 14:52
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