Stellar Magnetic Fields

In non-degenerate stars, magnetic fields are detected and measured through the Zeeman effect in stellar spectral lines, mainly using the polarization properties of Zeeman splitting. Such data may now be modelled amazingly accurately. In white dwarf stars, fields may be measured using spectral line methods up to similar to 10 MG (similar to 1 kT). Above this level one can also estimate the field from continuum circular (and sometimes linear) polarization, although we do not yet know how to model these correctly.