  The magnetic fields in the solar corona are generally neither force-free nor
axisymmetric and have complex dynamics that are difficult to characterize. Here
we simulate the topological evolution of solar coronal magnetic field lines
(MFLs) using a magnetohydrodynamic model. The simulation is initialized with a
non-axisymmetric non-force-free magnetic field that best correlates with the
observed vector magnetograms of solar active regions (ARs). To focus on these
ideas, simulations are performed for the flaring AR 11283 noted for its
complexity and well-documented dynamics. The simulated dynamics develops as the
initial Lorentz force pushes the plasma and facilitates successive magnetic
reconnections at the two X-type null lines present in the initial field.
Importantly, the simulation allows for the spontaneous development of mass
flow, unique among contemporary works, that preferentially reconnects field
lines at one of the X-type null lines. Consequently, a flux rope consisting of
low-lying twisted MFLs, which approximately traces the major polarity inversion
line, undergoes an asymmetric monotonic rise. The rise is attributed to a
reduction in the magnetic tension force at the region overlying the rope,
resulting from the reconnection. A monotonic rise of the rope is in conformity
with the standard scenario of flares. Importantly, the simulated dynamics leads
to bifurcations of the flux rope, which, being akin to the observed filament
bifurcation in AR 11283, establishes the appropriateness of the initial field
in describing ARs.
