A Statistical Study on Photospheric Magnetic Nonpotentiality of Active Regions and Its Relationship with Flares during Solar Cycles 22-23

摘要

A statistical study is carried out on the photospheric magneticnonpotentiality in solar active regions and its relationship with associatedflares. We select 2173 photospheric vector magnetograms from 1106 activeregions observed by the Solar Magnetic Field Telescope at Huairou SolarObserving Station, National Astronomical Observatories of China, in the periodof 1988-2008, which covers most of the 22nd and 23rd solar cycles. We havecomputed the mean planar magnetic shear angle (\bar{\Delta\phi}), mean shearangle of the vector magnetic field (\bar{\Delta\psi}), mean absolute verticalcurrent density (\bar{|J_{z}|}), mean absolute current helicity density(\bar{|h_{c}|}), absolute twist parameter (|\alpha_{av}|), mean free magneticenergy density (\bar{\rho_{free}}), effective distance of the longitudinalmagnetic field (d_{E}), and modified effective distance (d_{Em}) of eachphotospheric vector magnetogram. Parameters \bar{|h_{c}|}, \bar{\rho_{free}},and d_{Em} show higher correlation with the evolution of the solar cycle. ThePearson linear correlation coefficients between these three parameters and theyearly mean sunspot number are all larger than 0.59. Parameters\bar{\Delta\phi}, \bar{\Delta\psi}, \bar{|J_{z}|}, |\alpha_{av}|, and d_{E}show only weak correlations with the solar cycle, though the nonpotentialityand the complexity of active regions are greater in the activity maximumperiods than in the minimum periods. All of the eight parameters show positivecorrelations with the flare productivity of active regions, and the combinationof different nonpotentiality parameters may be effective in predicting theflaring probability of active regions.