Partially ionized hydrogen plasma in strong magnetic fields

We study the thermodynamic properties of a partially ionized hydrogen plasm a in strong magnetic fields, B similar to 10(12)-10(13) G, typical of neutr on stars. The properties of the plasma depend significantly on the quantum- mechanical sizes and binding energies of the atoms, which are strongly modi fied by thermal motion across the field. We use new fitting formulas for th e atomic binding energies and sizes, based on accurate numerical calculatio ns and valid for any state of motion of the atom. In particular, we take in to account decentered atomic states, neglected in previous studies of therm odynamics of magnetized plasmas. We also employ analytic fits for the therm odynamic functions of nonideal fully ionized electron-ion Coulomb plasmas. This enables us to construct an analytic: model of the free energy. An ioni zation equilibrium equation is derived, taking into account the strong magn etic field effects and the: nonideality effects. This equation is solved by an iteration technique. Ionization degrees, occupancies, and the equation of state are calculated. [S1063-651X(99)01308-2].