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H. Ji (BBSO/NJIT), M. Song (Purple Mountain Observatory, China), H. Wang (BBSO/NJIT)
In this paper, a newly developed method is presented for calculating linear force free coronal magnetic field that is consistent with the observed three components of the magnetic field. In terms of linear equation theory, the solutions are given in an integration form which consists of two parts: source functions and a Green function. Instead of using the observed magnetic field as the source function, we use totally six unknown source functions. By making the force-free field match the three components of the magnetic field of a magnetogram, we get a set of linear algebraic equations from which the source functions are solved out. We use the well-known boundary finite element method to discretize the integration solutions.
Since the computed magnetic fields decrease very rapidly, we use only one thin layer of the computed fields, and then use the fields' values on the top plane of this layer as boundary conditions of next thin layer. This stratification computing method is tested by applications to a known linear force free field with a quadrupolar configuration and an observed magnetogram by BBSO. Also, this method is compared with other methods. The testing and comparing results show that the method is reliable.
This work is supported by NSF under grants ATM-0076602, ATM-9903515 and ATM-0086999, NASA under grants NAG5-9682, NAG5-9738 and NAG5-10910, and ONR under grant N00014-97-1-1037.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.