On the problem of additional sources of microwave radiation in space plasma

We discuss possible additional mechanisms of microwave radiation in the dusty space plasma associated with the electron–ion recombination on the surface of grains that have to be taken into account in general balance of radiation. It is assumed that the Coulomb-type bound states of electrons exist on the surface of dusty particles. The recombination of plasma ions with electrons in these states forms neutral excited atoms (Rydberg atoms). Their quantum states depend on the dielectric permittivity of the grains and the quantum state of the electron on the surface. Spontaneous quantum transitions of the Rydberg atoms to the states with lower energies may be considered as an additional source of infrared radiation. dberg atoms with energies closed to zero (near the ionization threshold) in a constant magnetic field may radiate cyclotron radiation