Modeling of Solar Atmosphere Parameters Above Sunspots Using RATAN-600 Microwave Observations by A.G. Stupishin et al.*15 May 2018, 09:14 UTC
Models of the upper transition region of sunspots have been derived based on the observed radio spectrum between 3 and 18 GHz from Radio Astronomical Telescope of the Academy of Sciences 600 (RATAN-600) observations. Our objective is to match the spectrum to show that, within the limits of the one-dimensional observations and modeling, we have obtained a reasonable description of the upper transition-region structure of sunspots. We have developed a diagnostic method, described below.
Method and results
Among all quasi-stationary solar structures the atmosphere over sunspots is characterized by the most extreme values of the temperature gradients and magnetic fields. Use of the radio band eliminates such difficulties as the solution of non-LTE transfer equations and inaccurate ion abundances. The system can be considered in thermal equilibrium because the measurements are in the Rayleigh–Jeans regime. This means that measured brightness temperatures of the microwave emission in the optically thick atmosphere actually represent the thermal electron temperatures. At centimeter wavelengths, the main contribution to the sunspot emission is a gyroresonance (GR) mechanism. Bright, optically thick GR radiation is mainly generated at the second and third harmonics of the gyrofrequency of ordinary and extraordinary modes.
A recent upgrade of RATAN-600 radio telescope ...