Solar Obsevations on RT-7.5 Bauman Moscow State Technical University Radio Telescope and Modeling of Millimeter Emission of 02.04.2017 Solar Flare

Presently, in the territory of Russia active millimeter solar observations are under way via Bauman Moscow State Technical University (BMSTU) RT-7.5 radio telescope (Shustikov et al., 2015, Smirnova et al., 2016; Rozanov 1981; Smirnova et al., 2013; Ryzhov et al., 2014). Rozanov 1981; Smirnova et al. 2013; Рыжов и др. 2014). A radio telescope antenna of the 7.75 m diameter with its unique receiving equipment mounted for frequencies of 93 and 140 GHz, (3.2 and 2.2 mm) allows observing the Sun in the mode of tracking area, or scanning, simultaneously at two frequencies. Such observations are a source of the most valuable information on flares - the most powerful solar activity effects. It is impossible to understand a nature of the energy release mechanisms in the solar flares when there is no adequate diagnosis of physical parameters of plasma and magnetic fields. Meanwhile, sub-THz (0.1-1 THz) radio observations make it possible to diagnose the most inaccessible areas for the Sun researchers, i.e. the chromosphere. The ground-based observations in the millimeter range are rare because of high sensitivity requirements for receiving equipment and significant atmosphere disturbances, while the appropriate space projects are just under development. The paper objective is to investigate a nature of the sub-THz emission from the flare with the positive spectral tilt recorded on the RT-7.5 radio telescope on April 2, 2017. To solve this problem, we used observations in the x-ray, ultraviolet, and microwave ranges. Based on the model of the flare Machado et.al. (1980) Chromosphere, a coronal plasma contribution to the millimeter radio emission has been estimated. This approach allows us not only to take a fresh look at the results obtained earlier, but also makes it possible to diagnose in-depth the physical parameters of the flare plasma.