A Nonlinear Force-Free Magnetic Field Approximation Suitable for Fast Forward-Fitting to Coronal Loops. II. Numeric Code and Tests

摘要: Based on a second-order approximation of nonlinear force-free magnetic field solutions in terms uniformly twisted lines derived Paper I, we develop here numeric code that is capable to forward-fit such analytical arbitrary magnetogram (or vector magnetograph) data combined with (stereoscopically triangulated) coronal loop 3D coordinates. We test the by forward-fitting six potential and nonpotential cases simulated our model, as well an exactly solution Low Lou (Astrophys. J. 352, 343, 1990) model. The tests demonstrate: i) satisfactory convergence behavior (with typical misalignment angles μ≈1∘ – 10∘), ii) relatively fast computation times (from seconds few minutes), iii) high fidelity retrieved α-parameters (α fit/α model≈0.9 1.0 for simulations α model≈0.7±0.3 model). salient feature this quasi-force-free field, which closely matches geometry loops active regions, complements existing (NLFFF) codes based photospheric magnetograms without constraints.