  In order to understand the flare trigger mechanism, we conducted
three-dimensional magnetohydrodynamic simulations using a coronal magnetic
field model derived from data observed by the Hinode satellite. Several types
of magnetic bipoles were imposed into the photospheric boundary of the
Non-linear Force-Free Field (NLFFF) model of Active Region NOAA 10930 on 2006
December 13 to investigate what kind of magnetic disturbance may trigger the
flare. As a result, we confirm that certain small bipole fields, which emerge
into the highly sheared global magnetic field of an active region, can
effectively trigger a flare. These bipole fields can be classified into two
groups based on their orientation relative to the polarity inversion line: the
so called opposite polarity (OP) and reversed shear (RS) structures as it was
suggested by Kusano et al. (2012). We also investigated the structure of the
footpoints of reconnected field lines. By comparing the distribution of
reconstructed field lines and the observed flare ribbons, the trigger structure
of the flare can be inferred. Our simulation suggests that the data-constrained
simulation taking into account both the large-scale magnetic structure and the
small-scale magnetic disturbance such as emerging fluxes is a good way to find
out a flare productive active region for space weather prediction.
