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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A statistical study on rotating sunspots: Polarities, rotation directions, and helicities
Xiaoli Yan,Z. Q. Qu,C. L. Xu +2 more
TL;DR: In this article, the number of rotating sunspots with clockwise rotation is approximately the same as the number with counterclockwise rotation in both hemispheres, while in the southern hemisphere the situation is almost reversed.
Journal ArticleDOI
The May 13, 2005 Eruption: Observations, Data Analysis and Interpretation
TL;DR: In this paper, the authors present detailed description and analysis of the May 13, 2005 eruption, the corresponding coronal mass ejection (CME) and intense geomagnetic storm observed near the Earth on May 15, 2005.
Journal ArticleDOI
Three-Dimensional Magnetic Restructuring in Two Homologous Solar Flares in the Seismically Active NOAA AR 11283
Chang Liu,Na Deng,Jeongwoo Lee,Jeongwoo Lee,Thomas Wiegelmann,Chaowei Jiang,Brian R. Dennis,Yang Su,Alina Donea,Haimin Wang +9 more
TL;DR: In this article, the authors carried out a comprehensive investigation comparing the three-dimensional magnetic field restructuring, flare energy release, and the helioseismic response of two homologous flares, the 2011 September 6 X2.1 (FL1) and September 7 X1.8 (FL2) flares in NOAA AR 11283.
Journal ArticleDOI
Effect of polarimetric noise on the estimation of twist and magnetic energy of force-free fields
TL;DR: In this paper, the authors investigated the effect of polarimetric noise on the calculation of global {alpha} value and magnetic energy of an analytical bipole using the force-free field approximation.
Journal ArticleDOI
Very Fast and Accurate Azimuth Disambiguation of Vector Magnetograms
TL;DR: In this article, the authors presented a method for fast and accurate azimuth disambiguation of vector magnetogram data regardless of the location of the analyzed region on the solar disk.
References
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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
TL;DR: The Solar Oscillations Investigation (SOI) as mentioned in this paper uses the Michelson Doppler Imager (MDI) instrument to probe the interior of the Sun by measuring the photospheric manifestations of solar oscillations.
Journal ArticleDOI
Latitudinal variation of helicity of photospheric magnetic fields
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