Nauka i Obrazovanie (Jan 2016)
Analysis of Hard X-Ray, Microwave and Millimeter Emission in Solar Flare Plasma on 5 July 2012
Abstract
Bauman Moscow State Technical University’s (BMSTU’s) radiotelescope RT-7.5 is in continuous operation to observe the active regions on the Sun at frequencies of 93 and 140 GHz (3.2 and 2.2 mm, respectively). A special attention is focused on the observations of solar flares. The given frequency range is understudied, but it allows us to have the unique information about the physical parameters of the chromospheric plasma of flare loops (Shustikov et al. 2015). The paper is aimed at a detailed study and interpretation of the characteristic features of the spectrum of solar flare radio emission observed using the BMSTU radio telescope RT-7.5 at frequencies of 93 and 140 GHz in case there is a radio flux density growth with frequency. A positive slope of the sub-THz spectrum of radio emission was earlier observed only from time to time at frequencies of 200 and 400 GHz (Kaufmann et al., 2009). Currently, the interpretation of this effect is still under discussion due to a lack of sufficient observational material with the desired frequency resolution in the sub-THz range (Krucker et al., 2013). The paper, using the July 5, 2012 flare event of X-class GOES M6.1 as an example, through numerical simulation of the radio flux density spectrum shows that the observed positive spectral slope of this flare between the frequencies of 93 and 140 GHz can be explained by available single population of low- and high-energy electrons, the generation of which occurs in the solar chromosphere-transition region of the Sun. It could be suggested that the effective Science & Education of the Bauman MSTU 95 electron acceleration occurs in the chromosphere, rather than, as previously thought, only at the coronal level. The section 1 briefly describes the observational data and methods of their obtaining and processing. The section 2 presents the main result of numerical modelling of the radio spectrum. The section 3 offers discussion of results and conclusions. The work was completed under support of the Russian Science Foundation Grant 16-12- 10448 and partly under support of the Grants 15-02-08028 A and 16-32-00535 of the Russian Foundation for Fundamental Research.
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