Abstract
Radiation processes are discussed for astrophysical hot plasmas in particular attention to nonequilibrium ionization. We consider typical two cases, ionizing condition attained for a shock-heated tenuous plasma of a supernova remnant and recombining condition for an X-ray irradiated plasma surrounding a neutron star. The former (latter) is characterized by the ionization degree lower (higher) than that expected for the collisional ionization equilibrium. Emission spectra from such plasmas are affected by secondary emission processes following ionization/recombination as well as by the deviation of relative ion abundances from their equilibrium values.
