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

Markus J. Aschwanden   Submitted: 2012-07-11 14:05

Based on a second-order approximation of nonlinear force-free magnetic field solutions in terms of uniformly twisted field lines derived in Paper I, we develop here a numeric code that is capable to forward-fit such analytical solutions to arbitrary magnetogram (or vector magnetograph) data combined with (stereoscopically triangulated) coronal loop 3D coordinates. We test the code here by forward-fitting to six potential field and six nonpotential field cases simulated with our analytical model, as well as by forward-fitting to an exactly force-free solution of the Low and Lou (1990) model. The forward-fitting tests demonstrate: (i) a satisfactory convergence behavior (with typical misalignment angles of mu approx 1°-10°), (ii) relatively fast computation times (from seconds to a few minutes), and (iii) the high fidelity of retrieved force-free α -parameters ( α m fit α m model approx 0.9-1.0 for simulations and α m fit α m model approx 0.7pm0.3 for the Low and Lou model). The salient feature of this numeric code is the relatively fast computation of a quasi-forcefree magnetic field, which closely matches the geometry of coronal loops in active regions, and complements the existing {sl nonlinear force-free field (NLFFF)} codes based on photospheric magnetograms without coronal constraints.

Authors: Markus J. Aschwanden and Anna Malanushenko
Projects: STEREO

Publication Status: Solar Physics (in press)
Last Modified: 2012-07-12 09:38
Go to main E-Print page  First 3D Reconstructions of Coronal Loops with the STEREO                 A+B Spacecraft: IV. Magnetic Modeling with Twisted Force-Free Fields  A Nonlinear Force-Free Magnetic Field Approximation         Suitable for Fast Forward-Fitting to Coronal Loops. I. Theory  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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