Gyroresonance and Free–Free Radio Emissions from Multithermal Multicomponent Plasma

The solar atmosphere contains thermal plasma at a wide range of temperatures. This plasma is often quantified, in both observations and models, by a differential emission measure (DEM). The DEM is a distribution of the thermal electron density squared over temperature. In observations, the DEM is computed along a line of sight, while in the modeling it is over an elementary volume element (voxel). This description of the multithermal plasma is convenient and widely used in the analysis and modeling of extreme ultraviolet emission, which has an optically thin character. However, there is no corresponding treatment in the radio domain, where the optical depth of emission can be large, more than one emission mechanism is involved, and plasma effects are important. Here, we extend the theory of thermal gyroresonance and free–free radio emissions in the classical single-temperature Maxwellian plasma to the case of a multitemperature plasma. The free–free component is computed using the DEM and temperature-dependent ionization states of coronal ions, contributions from collisions of electrons with neutral atoms, the exact Gaunt factor, and the magnetic field effect. For the gyroresonant component, another measure of the multitemperature plasma is used, which describes the distribution of the thermal electron density over temperature. We give representative examples demonstrating important changes in the emission intensity and polarization due to the effects considered. The theory is implemented in available computer code.