Abstract

Force-free magnetic fields, in which the magnetic or Lorentz force is self-balancing and hence zero, provide a simple model for fields in the Sun’s corona. In principle the model may be solved using boundary values of the field derived from observations, e.g. data from the Hinode spectro-polarimeter. In practise the boundary data is inconsistent with the model, because fields at the photospheric level are subject to non-magnetic forces, and because of substantial uncertainties in the boundary data. The ‘self-consistency’ procedure (Wheatland & Régnier 2009) provides an approach to resolving the problem. This talk reports on results achieved with the procedure, in particular new results obtained for active region AR 10953 using Hinode data incorporating uncertainties in the boundary conditions (Wheatland & Leka 2011).