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
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Journal ArticleDOI
He I vector magnetic field maps of a sunspot and its superpenumbral fine-structure
TL;DR: In this paper, the authors derived the equilibrium magnetic structure of a sunspot in the chromosphere, and further showed that the superpenumbral magnetic field does not appear finely structured, unlike the observed intensity structure.
Journal ArticleDOI
Estimating Electric Current Densities in Solar Active Regions
TL;DR: In this paper, a force-free model of the magnetic field in solar active regions is proposed to estimate the electric current densities at the photosphere from vector magnetogram data subject to substantial uncertainties.
Journal ArticleDOI
Constraining the magnetic vector in the quiet solar photosphere and the impact of instrumental degradation
R. J. Campbell,Sergiy Shelyag,C. Quintero Noda,Mihalis Mathioudakis,Peter H. Keys,Aaron Reid +5 more
TL;DR: In this paper, the Stokes Inversions based on Response Functions (SIR) code is used to produce synthetic observables in the same near infrared spectral window as observed by the GREGOR Infrared Spectrograph (GRIS), which contains the highly magnetically sensitive photospheric Fe I line pair at 15.52 A and 15.87 A.
Journal ArticleDOI
Spectropolarimetric analysis of an active region filament. I. Magnetic and dynamical properties from single component inversions
TL;DR: In this article, the magnetic filed vector of an active region filament was determined by interpreting the Hanle and Zeeman effects in suitable chromospheric spectral lines like those of the He I multiplet at 10830 A.
Journal ArticleDOI
Spectropolarimetric evidence for a siphon flow along an emerging magnetic flux tube
Iker S. Requerey,Iker S. Requerey,B. Ruiz Cobo,B. Ruiz Cobo,J. C. del Toro Iniesta,D. Orozco Suárez,J. Blanco Rodríguez,Sami K. Solanki,Sami K. Solanki,Peter Barthol,Achim Gandorfer,Laurent Gizon,Laurent Gizon,Johann Hirzberger,Tino L. Riethmüller,M. van Noort,W. Schmidt,V. Martínez Pillet,M. Knölker +18 more
TL;DR: In this article, the authors studied the dynamics and topology of an emerging magnetic flux concentration using high spatial resolution spectropolarimetric data acquired with the Imaging Magnetograph eXperiment on board the Sunrise balloon-borne solar observatory.
References
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Book ChapterDOI
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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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