The temporal evolution of thermal bremsstrahlung in the sub-terahertz range is calculated for F-CHROMA models of the flare chromosphere and transition region (https://www.fchroma.org). These models are calculated based on the numerical solution of the system of equations of radiation hydrodynamics with the RADYN code, which describes the response of chromospheric plasma to the flux of accelerated electrons in the form of a triangular pulse. It is found that the positive slope of the spectrum in the frequency range of 93–400 GHz is formed during the entire burst. The sub-THz radiation peak can be both ahead and behind the maximum of the function of the injection of energetic electrons depending on the number and index of the spectrum of precipitating particles. In some cases, the time profile of the sub-THz radiation is quite complex and pulsating due to gas-dynamic phenomena in the chromosphere and transition region.
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This study was supported in part by the Russian Foundation for Basic Research, project no. 18-02-00856-a; Ministry of Science and Higher Education of the Russian Federation, project no. 0831-2019-0006; Ministry of Science and Higher Education of the Russian Federation, project no. RFMEFI62020X0003 and project nos. RVO:67985815 and LM2015067: EU-ARC.CZ.
The authors declare that they have no conflict of interest.
Translated by O. Pismenov
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Morgachev, A.S., Tsap, Y.T., Smirnova, V.V. et al. Numerical Simulation of Sub-Terahertz Thermal Emission: RADYN Code. Geomagn. Aeron. 60, 1038–1049 (2020). https://doi.org/10.1134/S0016793220080174