An MHD Simulation of AR11944 Using Hmi Magnetic Field Data

Friday, 19 December 2014
Keiji Hayashi, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
We will present the results from the MHD simulation of the active region 11944 using series of the HMI magnetic field data as time-varying boundary condition on the solar photosphere.

Our simulation model applies the concept of the characteristics, as in our previous studies, to all boundary surfaces, so that the influences of unphysical waves from outside will be prevented from entering the simulation domain. To the bottom boundary, specifically, the boundary treatments are applied so that the enforced time-evolution of the normal component of magnetic field satisfying the characteristics equations of the hyperbolic MHD system and preserving the divergence-free condition in the simulated volume.

In this numerical chamber carefully prepared, we first set the potential field as the initial values of the magnetic field; then, the observation-based time-dependent boundary values will drive the system to form regions of twisted field lines with higher magnetic energy density than the initial potential field.

We applied our model to the region 11944 and conducted a simulation, for a 24-hour span from 2014 January 6, 23 UT to examine the evolution of the magnetic field structures and accumulation of magnetic energy in the simulated system before and after an X flare (around Jan. 7 18 UT).