Radiation hydrodynamics in a moving plasma with Compton scattering: Frequency-dependent solutions.

This article focuses on deriving analytical solutions to frequency-dependent radiative moment equations for hot plasmas undergoing Compton scattering within the subrelativistic regime, defined by electron temperature \( k_B T / (m_e c^2) \lesssim 0.1 \), photon frequency \( h \nu / (m_e c^2) \lesssim 0.1 \), and fluid velocity \( v / c \lesssim 0.1 \). Ignoring induced scattering terms, the study obtains Wien-type and power-law-type solutions for both static plane-parallel atmospheres and accelerating one-dimensional plasma flows, incorporating bulk Compton effects in the latter. Notably, in moving plasmas, the radiation field gains momentum from the plasma at low photon energies (\( h \nu < 3 k_B T \)) but loses momentum at higher energies (\( h \nu > 3 k_B T \)). These solutions extend classical Milne–Eddington results into regimes including Comptonization and provide a foundation for further semi-analytical treatments of radiation hydrodynamics with Compton scattering in astrophysical contexts.