Latitude Variation of Helicity in Solar Active Regions

We studied the current helicity of 230 active regions on the Sun during the period of 1992-2001. Vector magnetograms used were obtained with the Solar Flare Telescope, located at the Mitaka campus of the National Astronomical Observatory. The latitude distribution of helicity shows a negative slope; namely, the regions in the northern (southern) hemisphere tend to show a negative (positive) helicity, respectively, in agreement with previous studies. The scatter seen in the helicity is significantly larger than expected from the measurement errors, implying that the process generating the helicity is of random, turbulent nature. Therefore, convective motion must play an essential role in generating the helicity of active regions.