Magneto-Frictional Modeling of Coronal Nonlinear Force-Free Fields. Ii. Application to Observations

Abstract

A magneto-frictional module has been implemented and tested in the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC) in the first paper of this series. Here, we apply the magneto-frictional method to observations to demonstrate its applicability in both Cartesian and spherical coordinates, and in uniform and block-adaptive octree grids. We first reconstruct a nonlinear force-free field (NLFFF) on a uniform grid of 180 3 cells in Cartesian coordinates, with boundary conditions provided by the vector magnetic field observed by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) at 06:00 UT on 2010 November 11 in active region NOAA 11123. The reconstructed NLFFF successfully reproduces the sheared and twisted field lines and magnetic null points. Next, we adopt a three-level block-adaptive grid to model the same active region with a higher spatial resolution on the bottom boundary and a coarser treatment of regions higher up. The force-free and divergence-free metrics obtained are comparable to the run with a uniform grid, and the reconstructed field topology is also very similar. Finally, a group of active regions, including NOAA 11401, 11402, 11405, and 11407, observed at 03:00 UT on 2012 January 23 by SDO/HMI is modeled with a five-level block-adaptive grid in spherical coordinates, where we reach a local resolution of  0 . 06 pixel −1 in an area of 790 Mm×604 Mm. Local high spatial resolution and a large field of view in NLFFF modeling can be achieved simultaneously in parallel and block-adaptive magneto-frictional relaxations.

Transition from Circular-ribbon to Parallel-ribbon Flares Associated with a Bifurcated Magnetic Flux Rope

“…The conditions of divergence-freeness and force-freeness are acceptable in applications of the method to observations. The two metrics in our results are similar to previous studies (e.g., Schrijver et al 2008;Yang et al 2015;Guo et al 2016b).…”

“…Guo et al (2016a) added the magneto-frictional module into MPI-AMRVAC and tested it with analytic solutions in both Cartesian and spherical coordinates. Guo et al (2016b) have successfully applied the method to observations in both Cartesian and spherical coordinates using the vector magnetic field observed by SDO/HMI. This method only considers force-free field approximation with dissipation expressed as a friction form in the momentum equation.…”

Origin and structures of solar eruptions II: Magnetic modeling

“…The background image is a 171Å image by SDO/AIA. The figure is from Guo et al (2016a) and reproduced by permission of the AAS. d. Colored solid lines show a twisted magnetic flux rope modeled by the magneto-frictional method in the spherical coordinate system with an adaptive mesh refinement.…”

“…The background image represents the radial magnetic field. The figure is adapted from Guo et al (2016a) and reproduced by permission of the AAS. Guo et al (2013b) and reproduced by permission of the AAS.…”

“…The solenoidal condition of the magnetic field is guaranteed by including a diffusive term in the induction equation. Guo et al (2016a) has applied the magneto-frictional method implemented in MPI-AMRVAC to the vector magnetic field observed by SDO/HMI in Cartesian coordinates with uniform or AMR grids and in spherical coordinates with AMR grids (Figures 2c and 2d).…”