Distribution of Photospheric Electric Current Helicity and Solar Activities

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Abstract
In this paper, we describe the distribution of photospheric current helicity of active regions in the solar surface. The sign of helicity is mainly negative in the northern hemisphere of the Sun and positive in the southern hemisphere. We also discuss the relationship between the current helicity parameter B∥ (∇ × B)∥ and the α-factor of the force-free field. Our observations show that active regions with current helicity signs opposite to most others in the same hemispheres occur normally at some heliographic longitudes and persist over long periods.In addition, we analyze a possible mechanism of the sign rule of current helicity that shows opposite signs in both hemispheres.