Making global map of the solar surface Br from the HMI vector magnetic field observations

The three-component solar surface magnetic field vector data are from the HMI observations with the data process pipeline modules, VFISV (Very Fast Inversion of the Stokes Vector, Borrero et al., 2011) for Milne-Eddington inversion and the minimum-energy disambiguation algorithm (Metcalf 1994, Leka et al, 2009).

The models of the global corona and solar wind, such as the PFSS (potential-field source-surface) model and the MHD simulations, often use the maps of solar surface magnetic field, especially the radial component (Br) as the boundary condition. The HMI observation can provide new Br data for these model. Because of weak magnetic signals at the quiet regions of the Sun, the limb darkening, and geometric effects near solar poles, we need to apply an assumption to make a whole-surface map.