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Currently there is a concern about ability of the classical thermal(Maxwellian) distribution to describe quasi-steady-state plasma in solaratmosphere including active regions. In particular, other distributions havebeen proposed to better fit observations, for example, kappa- and$n$-distributions. If present, these distributions will generate radioemissions with different observable properties compared with the classicalgyroresonance (GR) or free-free emission, which implies a way of remotedetecting these non-Maxwellian distributions in the radio observations. Here wepresent analytically derived GR and free-free emissivities and absorptioncoefficients for the kappa- and $n$-distributions and discuss their properties,which are in fact remarkably different from each other and from the classicalMaxwellian plasma. In particular, the radio brightness temperature from agyrolayer increases with the optical depth $\tau$ for kappa-distribution, butdecreases with $\tau$ for $n$-distribution. This property has a remarkableconsequence allowing a straightforward observational test: the gyroresonanceradio emission from the non-Maxwellian distributions is supposed to benoticeably polarized even in the optically thick case, where the emission wouldhave strictly zero polarization in the case of Maxwellian plasma. This offers away of remote probing the plasma distribution in astrophysical sourcesincluding solar active regions as a vivid example.

Theory of gyroresonance and free-free emissions from non-Maxwellian quasi-steady-state electron distributions