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Magnetic Nonpotentiality in Photospheric Active Regions as a Predictor of Solar Flares  

Xiao Yang   Submitted: 2013-08-06 19:17

Based on several magnetic nonpotentiality parameters obtained from the vector photospheric active region magnetograms obtained with the Solar Magnetic Field Telescope at the Huairou Solar Observing Station over two solar cycles, a machine learning model has been constructed to predict the occurrence of flares in the corresponding active region within a certain time window. The Support Vector Classifier, a widely used general classifier, is applied to build and test the prediction models. Several classical verification measures are adopted to assess the quality of the predictions. We investigate different flare levels within various time windows, and thus it is possible to estimate the rough classes and erupting times of flares for particular active regions. Several combinations of predictors have been tested in the experiments. The True Skill Statistics are higher than 0.36 in 97% of cases and the Heidke Skill Scores range from 0.23 to 0.48. The predictors derived from longitudinal magnetic fields do perform well, however they are less sensitive in predicting large flares. Employing the nonpotentiality predictors from vector fields improves the performance of predicting large flares of magnitude geqM5.0 and geqX1.0.

Authors: Xiao Yang, GangHua Lin, HongQi Zhang, XinJie Mao
Projects:

Publication Status: ApJL 774 (2013) L27
Last Modified: 2013-08-28 14:58
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A Statistical Study on Photospheric Magnetic Nonpotentiality of Active Regions and Its Relationship with Flares During Solar Cycles 22 - 23  

Xiao Yang   Submitted: 2012-07-26 22:37

A statistical study is carried out on the photospheric magnetic nonpotentiality in solar active regions and its relationship with associated flares. We select 2173 photospheric vector magnetograms from 1106 active regions observed by the Solar Magnetic Field Telescope at Huairou Solar Observing Station, National Astronomical Observatories of China, in the period of 1988 - 2008, which covers most of the 22nd and 23rd solar cycles. We have computed the mean planar magnetic shear angle (overline{Deltaphi}), mean shear angle of the vector magnetic field (overline{Deltapsi}), mean absolute vertical current density (overline{|Jz|}), mean absolute current helicity density (overline{|hc|}), absolute twist parameter ( α av|), mean free magnetic energy density (overline{ hofree}), effective distance of the longitudinal magnetic field (dE), and modified effective distance (dEm) of each photospheric vector magnetogram. Parameters overline{|hc|}, overline{ hofree}, and dEm show higher correlations with the evolution of the solar cycle. The Pearson linear correlation coefficients between these three parameters and the yearly mean sunspot number are all larger than 0.59. Parameters overline{Deltaphi}, overline{Deltapsi}, overline{|Jz|}, α av|, and dE show only weak correlations with the solar cycle, though the nonpotentiality and the complexity of active regions are greater in the activity maximum periods than in the minimum periods. All of the eight parameters show positive correlations with the flare productivity of active regions, and the combination of different nonpotentiality parameters may be effective in predicting the flaring probability of active regions.

Authors: Xiao Yang, HongQi Zhang, Yu Gao, Juan Guo and GangHua Lin
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Publication Status: Solar Phys. 280 (2012) 165-181
Last Modified: 2013-08-06 19:18
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Magnetic Nonpotentiality in Photospheric Active Regions as a Predictor of Solar Flares
A Statistical Study on Photospheric Magnetic Nonpotentiality of Active Regions and Its Relationship with Flares During Solar Cycles 22 - 23

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