  Seven different models are applied to the same problem of simulating the
Sun's coronal magnetic field during the solar eclipse on 2015 March 20. All of
the models are non-potential, allowing for free magnetic energy, but the
associated electric currents are developed in significantly different ways.
This is not a direct comparison of the coronal modelling techniques, in that
the different models also use different photospheric boundary conditions,
reflecting the range of approaches currently used in the community. Despite the
significant differences, the results show broad agreement in the overall
magnetic topology. Among those models with significant volume currents in much
of the corona, there is general agreement that the ratio of total to potential
magnetic energy should be approximately 1.4. However, there are significant
differences in the electric current distributions; while static extrapolations
are best able to reproduce active regions, they are unable to recover sheared
magnetic fields in filament channels using currently available vector
magnetogram data. By contrast, time-evolving simulations can recover the
filament channel fields at the expense of not matching the observed vector
magnetic fields within active regions. We suggest that, at present, the best
approach may be a hybrid model using static extrapolations but with additional
energization informed by simplified evolution models. This is demonstrated by
one of the models.
