Abstract
Abstract Current helicity and twist of solar magnetic fields are important in characterizing the dynamo mechanism working in the convection zone of the Sun. We have carried out a statistical study on the current helicity of solar active regions observed with the spectro-polarimeter (SP) of the Hinode Solar Optical Telescope (SOT). We used SOT-SP data of 558 vector magnetograms of a total of 80 active regions obtained during the period from 2006 to 2012. We have applied spatial smoothing and division of data points into weak and strong field ranges to compare the contributions from different scales and field strengths. We found that the current helicity follows the “hemispheric sign rule” when weak magnetic fields (absolute field strength < 300 gauss) are considered and no smoothing is applied. On the other hand, the pattern of current helicity fluctuates and violates the hemispheric sign rule when stronger magnetic fields are considered and smoothing of 2${^{\prime\prime}_{.}}$0 (modeled on ground-based observations) is applied. Furthermore, we found a tendency that weak and inclined fields conform to the hemispheric sign rule and strong and vertical fields violate it. These different properties of helicity through the strong and weak magnetic field components give important clues in understanding the solar dynamo as well as the mechanism of formation and evolution of solar active regions.
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