Long-term variation of sunspot latitudes

We consider a continuous sunspot data set ranging from 1853 to 1996. The em phasis is given to long-term activity variations and north-south asymmetrie s. The difference of the distance between sunspot belts and equator between the northern and southern hemispheres is considered and a systematic varia tion is found. The period of this variation is about 8.4 sunspot cycles or about 90 years, and the amplitude is 1.3 degrees. This phenomenon could be explained by oscillation of a quadrupolar component of solar mixed parity m ode magnetic field.