  We present a new magnetic-atmosphere model code for obtaining synthetic
spectral fluxes of hydrogen-rich magnetic white dwarfs. To date, observed
spectra have been analyzed with models that neglect the magnetic field's
effects on the atomic populations. In this work, we incorporate state-of-art
theory in the evaluation of numerical densities of atoms, free electrons, and
ions in local thermodynamical equilibrium under the action of a magnetic field.
The energy distribution of atoms is rigorously evaluated for arbitrary field
strength. This energy pattern includes going from tightly bound states to
metastable or truly bound, highly excited states embedded in the continuum,
that is, over the first Landau level. Finite nuclear mass effects and the
coupling between the internal atomic structure and the motion of the atom
across the magnetic field are also considered. Synthetic fluxes are generated
with integrations of numerical solutions of polarized radiative transfer over
the visible stellar disk using a spherical t-design method. The atmosphere code
is tested with observations from the Sloan Digital Sky Survey for a group of
known magnetic white dwarfs. Physical stellar parameters are obtained from
least-squares fits to the observed energy distribution and compared with
results of previous works. We show that the use of zerofield ionization
equilibrium in spectral analyses can lead to underestimated effective
temperatures for highly magnetic white dwarfs.
