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Astron. Astrophys. 339, 880-886 (1998)


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Latitudinal distribution of photospheric current helicity and solar activities

Hongqi Zhang and Shudong Bao

Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, P.R. China

Received 8 October 1997 / Accepted 24 April 1998

Abstract

In this paper, we analyze the latitudinal distribution of the photospheric current helicity for 422 active regions, including most of the large ones observed in the last ten years. Observations show that most active regions in the northern hemisphere have negative helicities and in the southern hemisphere have positive ones. The negative maximum values of current helicity occurred in 1989 and 1991, while those positive around 1992. It is evident that the observational current helicity of active regions is normally brought up by emerging magnetic flux from the subatmosphere and probably acted by the moving mass. The result observed shows that less than 20 [FORMULA] of active regions have the sign opposite to that of most ones in the same hemisphere. These reversed sign regions of the current helicity are obviously related to abnormal distribution of the vector magnetic field in the active regions, due to emergence of new magnetic flux of opposite polarities.

Key words: Sun: activity – Sun: magnetic fields – Sun: photosphere


© European Southern Observatory (ESO) 1998

Online publication: October 22, 1998

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