5 Distribution of active regions with different chirality

Figures 2 and 3 show that most of the active regions in the northern/southern hemisphere have a positive/negative tilt angle and a negative/positive mean twist <h_||> of the magnetic field lines. These active regions are regarded as "normal active regions'' with "normal chirality'' due to adhering to both Joy's Law and the hemispheric helicity rule. While in some other active regions, as in Figs. 2 and 3, we see the sign of the tilt angle is the same as the sign of the mean twist <h_||>. These active regions disobey either Joy's Law or the hemispheric helicity rule. We regard these regions as "abnormal active regions'' with "abnormal chirality''. Our results show that in both the northern and southern hemisphere, about 60% of the active regions are of "normal chirality'', and about one-third of the active regions are of "abnormal chirality''.

In our data, there are a third kind of active region which has a negative/positive tilt angle with a positive/negative twist in the northern/southern hemisphere, i.e. adhering to neither Joy's Law nor the hemispheric helicity rule. They do not belong to either of the two groups defined above and are a tiny fraction of the active regions (less than 5%).

Figure 4: Longitudinal distribution of the active regions with Carrington rotation. The sign "+'' denotes active regions with a "normal chirality'', "-'' denotes active regions with an "abnormal chirality'', and "*'' denotes active regions with neither a "normal chirality'' nor an "abnormal chirality'' (see text). Each point indicates one active region.

In Fig. 4 we give the distribution of the studied active regions with Carrington rotation. In the figure, the sign "+'' denotes active regions with "normal chirality'', i.e., active regions with a positive/negative tilt angle $\varphi$ and a negative/positive twist < h_|| >of magnetic lines in the northern/southern hemisphere; "-'' denotes active regions with an "abnormal chirality'', i.e., active regions in which the tilt angle $\varphi$ and the mean twist < h_|| > have the same sign. The third kind of active region with a negative/positive tilt angle $\varphi$ and a positive/negative twist < h_|| > in the northern/southern hemisphere, which have neither a "normal chirality'' nor an "abnormal chirality'', are denoted by "*''. Figure 4 show that some areas keep the same sign for many rotations, implying that the helicity of the magnetic fields has been generated at great depths. This result is in agreement with Canfield & Pevtsov (1998). We especially find that those active regions with "abnormal chirality'', denoted by "-'' sign, tend to be located at some special heliospheric longitudes, such as 0-30$^\circ$, 120$^\circ$, 240$^\circ-$270$^\circ$and 330$^\circ-$360$^\circ$in the northern hemisphere and 30$^\circ-$90$^\circ$, 180$^\circ-$270$^\circ$ in the southern hemisphere.