  The coronal magnetic field evolution of 20 bipolar active regions (ARs) is
simulated from their emergence to decay using the time-dependent nonlinear
force-free field method of Mackay et al. A time sequence of cleaned
photospheric line-of-sight magnetograms, that covers the entire evolution of
each AR, is used to drive the simulation. A comparison of the simulated coronal
magnetic field with the 171 and 193 A observations obtained by the Solar
Dynamics Observatory (SDO)/ Atmospheric Imaging Assembly (AIA), is made for
each AR by manual inspection. The results show that it is possible to reproduce
the evolution of the main coronal features such as small- and large-scale
coronal loops, filaments and sheared structures for 80% of the ARs. Varying the
boundary and initial conditions, along with the addition of physical effects
such as Ohmic diffusion, hyperdiffusion and a horizontal magnetic field
injection at the photosphere, improves the match between the observations and
simulated coronal evolution by 20%. The simulations were able to reproduce the
build-up to eruption for 50% of the observed eruptions associated with the ARs.
The mean unsigned time difference between the eruptions occurring in the
observations compared to the time of eruption onset in the simulations was
found to be ~5 hrs. The simulations were particularly successful in capturing
the build-up to eruption for all four eruptions that originated from the
internal polarity inversion line of the ARs. The technique was less successful
in reproducing the onset of eruptions that originated from the periphery of ARs
and large-scale coronal structures. For these cases global, rather than local,
nonlinear force-free field models must be used. While the technique has shown
some success, eruptions that occur in quick succession are difficult to
reproduce by this method and future iterations of the model need to address
this.
