| Abstract: | An alternative parameter R_J_z is introduced as the ratio of one of two kinds of opposite-sign current to the total current and is used to investigate the relationship between this quantity and the hemispheric helicity sign rule(HSR) that has been established by a series of previous statistical studies. The classification of current in each hemisphere obeys the following rule: if the product of the current and the corresponding longitudinal field component contributes a consistent sign with respect to the HSR,it is called "HSR-compliant" current,otherwise it is called "HSR-noncompliant" current. Firstly,consistency between the butterfly diagram of R_J_z and current helicity was obtained in a statistical study.Active regions with R_J_zsmaller than 0.5 tend to obey the HSR whereas those with R_J_z greater than 0.5 tend to disobey it. The "HSR-compliant" current systems have a 60% probability of realization compared to 40% for "HSR-noncompliant" current systems. Overall,the HSR is violated for active regions in which the "HSR-noncompliant" current is greater than the "HSR-compliant" current. Secondly,the parameter R_J_z was subsequently used to study the evolution of current systems in the case analyses of flare-productive active regions NOAA AR 11158 and AR 11283. It is found that there is a "R_J_z-quasistationary" phase that is relatively flare quiescent and "R_J_z-dynamic" phase that is characterized by the occurrence of large flares. |
