  The physical interpretation of spectropolarimetric observations of lines of
neutral helium, such as those of the 10830 A multiplet, represents an excellent
opportunity for investigating the magnetism of plasma structures in the solar
chromosphere. Here we present a powerful forward modeling and inversion code
that permits either to calculate the emergent intensity and polarization for
any given magnetic field vector or to infer the dynamical and magnetic
properties from the observed Stokes profiles. This diagnostic tool is based on
the quantum theory of spectral line polarization, which self-consistently
accounts for the Hanle and Zeeman effects in the most general case of the
incomplete Paschen-Back effect regime. We also take into account radiative
transfer effects. An efficient numerical scheme based on global optimization
methods has been applied. Our Stokes inversion code permits a fast and reliable
determination of the global minimum.
