Journal ArticleDOI
An Overview of Existing Algorithms for Resolving the 180° Ambiguity in Vector Magnetic Fields: Quantitative Tests with Synthetic Data
Thomas R. Metcalf,K. D. Leka,Graham Barnes,Bruce W. Lites,Manolis K. Georgoulis,Alexei A. Pevtsov,Krishnan Balasubramaniam,G. Allen Gary,Ju Jing,Jing Li,Yang Liu,Huaning Wang,Valentyna Abramenko,Vasyl Yurchyshyn,Yong-Jae Moon +14 more
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TLDR
In this article, the authors report on the state-of-the-art in algorithms used for resolving the 180° ambiguity in solar vector magnetic field measurements and compare them quantitatively and seek to understand where each succeeds, where it fails and why.Abstract:
We report here on the present state-of-the-art in algorithms used for resolving the 180° ambiguity in solar vector magnetic field measurements. With present observations and techniques, some assumption must be made about the solar magnetic field in order to resolve this ambiguity. Our focus is the application of numerous existing algorithms to test data for which the correct answer is known. In this context, we compare the algorithms quantitatively and seek to understand where each succeeds, where it fails, and why. We have considered five basic approaches: comparing the observed field to a reference field or direction, minimizing the vertical gradient of the magnetic pressure, minimizing the vertical current density, minimizing some approximation to the total current density, and minimizing some approximation to the field's divergence. Of the automated methods requiring no human intervention, those which minimize the square of the vertical current density in conjunction with an approximation for the vanishing divergence of the magnetic field show the most promise.read more
Citations
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Journal ArticleDOI
Modeling Magnetic Field Structure of a Solar Active Region Corona Using Nonlinear Force-free Fields in Spherical Geometry
TL;DR: In this article, a nonlinear force-free field (NLFFF) optimization code in spherical geometry using an analytical solution from Low and Lou is presented. But the results show that the results are not applicable to the case where exact vector field data are provided on all boundaries, but only the lower boundary.
Journal ArticleDOI
Multiwavelength spectropolarimetric observations of an Ellerman bomb
Reza Rezaei,C. Beck +1 more
TL;DR: In this paper, the structure of an Ellerman bomb in the photosphere and chromosphere was studied. But the authors focused on the spectral properties of the EB and did not consider the effect of magnetic flux cancellation on the EB.
Journal ArticleDOI
Magneto-frictional modeling of coronal nonlinear force-free fields. ii. application to observations
TL;DR: In this paper, a magneto-frictional module has been implemented and tested in the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC).
Journal ArticleDOI
Local twist and current helicity distributions of active region noaa 10930
TL;DR: In this paper, high-quality vector magnetograms and G-band data are utilized to study the distributions of local twist alpha(z) and current helicity h(c) on the active region of NOAA 10930.
Journal ArticleDOI
Guiding nonlinear Force-Free Modeling Using Coronal Observations: First Results Using a Quasi Grad-Rubin scheme
Anna Malanushenko,Anna Malanushenko,Carolus J. Schrijver,Marc L. DeRosa,Michael S. Wheatland,S. A. Gilchrist +5 more
TL;DR: In this article, the authors developed and tested an algorithm to use images showing coronal loops in the modeling of the solar coronal magnetic field and applied a Grad-Rubin-like iterative technique to obtain a volume-filling nonlinear force free model of the magnetic field.
References
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Journal ArticleDOI
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Journal ArticleDOI
The Solar Oscillations Investigation - Michelson Doppler Imager
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Book ChapterDOI
The Solar Oscillations Investigation — Michelson Doppler Imager
Philip H. Scherrer,R. S. Bogart,R. I. Bush,J. T. Hoeksema,Alexander G. Kosovichev,Jesper Schou,W. Rosenberg,L. Springer,T. D. Tarbell,A. M. Title,C. J. Wolfson,I. Zayer +11 more
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Journal ArticleDOI
Latitudinal variation of helicity of photospheric magnetic fields
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