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Abstract—We present a method of determination of numbers of gyroresonance layers most effectively radiating in the transition region of the active solar atmosphere. It is based on determination of frequency in the spectrum of an extraordinary wave of an active region, at which the gradient of this spectrum abruptly rises. Observations of 29 active regions carried out at the RATAN-600 radio telescope have been analyzed. The magnetic field in the transition region was determined from the frequency of bending point in the spectrum of antenna temperatures in an extraordinary mode under condition of emission in the third harmonic of the gyrofrequency. The relation between the photospheric magnetic field strength and the magnetic field strength in the transition region (1.52–2.28) is substantially greater than previously obtained, namely, the field isdecreasedonlyby10–20% in the transition region. The heights in the transition region were determined from the reconstructed magnetic field in the nonlinear force-free approximation, and are in the range of 1.00–3.57 Mm. [ABSTRACT FROM AUTHOR]

The distributions of temperature and density in the sunspot atmosphere are crucial for an understanding of the process of energy transfer from the photosphere upward to the corona in strong magnetic fields. The joint analysis of millimeter observations at ALMA (Atacama Large Millimeter/Submillimeter Array) and observations performed in the microwave range (centimeter wavelengths) with the RATAN-600 radio telescope of the Russian Academy of Sciences provides new data on the temperature distribution and physical processes at different altitudes above a spot. The NOAA 12470 active region was observed and mapped at 1.3 and 3 mm (ALMA) and 2–10 cm (RATAN-600) in December 2015. These observations are analyzed, and the results are compared to models of sunspot atmospheres. The fundamental problems arising in the study of atmospheres of active regions in the millimeter and centimeter ranges are determined, and the importance of the 3–18 mm range in the physics of the generation and transfer of energy for corona heating is demonstrated. [ABSTRACT FROM AUTHOR]

We present the results of forecasting flare activity based on the data from microwave spectropolarimetric observations of active regions (ARs) obtained with the RATAN-600 radio telescope and the X-ray data from the GOES satellite as well as monitoring data. The method is designed for short-term (1-3-days) flare forecasts. Proton events are considered as part of the general flare problem. Obtaining a reliable forecast is a difficult process in view of the multi-parameter and multi-dimensional system of plasma parameter variations and multiple non-linear interconnections.We used a modified Tanaka-Enome criterion, as well a database of observational material collected over many years. The forecasting efficiency was analyzed depending on the threshold values of the criterion. We show that the quality of the radio astronomical forecast is determined by the level of sensitivity of the detector at short centimeterwavelengths and by the solar activity level. [ABSTRACT FROM AUTHOR]

High-altitude measurements and magnetic field distribution in active regions are always an important problem to verify existing models at heights from units to hundreds of Mm. Optical methods of analysis of the magnetic structure work well only at the photosphere level. At the same time, the progress of radio astronomy methods of analyzing the solar radio emission [1] and of the theory of solar plasma radiation [2] facilitates introduction of new methods for measuring the magnetic field strength at various altitudes in the solar atmosphere. In this paper we use multi-wave observations of polarization of the radio emission of active regions in the microwave range together with precise magnetosphere data in order to develop a method of projection for measuring the height distribution of the magnetic field. [ABSTRACT FROM AUTHOR]

Observations of the active region AR 7962 obtained at 2–32 cm on the RATAN-600 radio telescope on May 10–12, 1996, are presented. The high-resolution measurements detected a narrow feature near 8.5 cm against the background of the smooth spectrum of the local source associated with sunspots. This narrow-band emission is identified with a bright, pointlike, high-frequency source at 1.7 cm recorded on maps made using the Nobeyama radio telescope. The characteristics of the observed line (lifetime 3 days, brightness temperature of the order of several million Kelvin, relative width of about 10%) suggest that it can be explained as thermal cyclotron radiation at the third harmonic of the electron gyrofrequency from a compact source containing a dense, hot plasma; the corresponding higher frequency emission could be due to thermal Bremsstrahlung. Analysis of the RATAN-600 and Nobeyama data can be used to probe the magnetic field, kinetic temperature, and electron density in the radiation source in the corona. © 2000 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

We develope a method to compute the temperature and density structure along the line of sight by inversion of the differential emission measure (DEM), under the assumptions of stratification and hydrostatic equilibrium. We apply this method to the DEM obtained from the Atmospheric Imaging Assembly (AIA) observations and use the results, together with potential extrapolations of the photospheric magnetic field, to compute the microwave emission of three sunspots, which we compare with observations from the Academy of Sciences Radio Telescope - 600 (RATAN-600) radio telescope and the Nobeyama Radioheliograph (NoRH). Our DEM-based models reproduce very well the observations of the moderate-size spot on October 2011 and within 25% the data of a similar sized spot on March 2016, but predict too low values for the big spot of 14 April 2016. The latter is better fitted by a constant conductive flux atmospheric model which, however, cannot reproduce the peak brightness temperature of 4.7×106K and the shape of the source at the NoRH frequency. We propose that these deviations are due to the low intensity non-thermal emission associated to a moving pore and to an opposite polarity light bridge. We also find that the double structure of the big spot at high RATAN-600 frequencies can be interpreted in terms of the variation of the angle between the magnetic field and the line of sight along the sunspot. [ABSTRACT FROM AUTHOR]