LONG-TERM VARIATIONS OF THE TORSIONAL OSCILLATIONS OF THE SUN

We investigated long-term variations of the differential rotation of t he solar large-scale magnetic field on 1024 H alpha charts in the lati tude zones from +45 degrees to -45 degrees in the period 1915-1990. We used the expansion in terms of Walsh functions. It turns out that the rotation of the Sun becomes more rigid than average during the cycle maximum and the rotation is more differential during minimum. From 191 5 to 1990, 7 bands of faster- and 7 bands of slower-than-average rotat ion are revealed showing an 11-year period. These bands drift towards the equator: 45 degrees in 2.5 to 8 years. The time span of the bands varies from 4 to 6.8 years and is in anti-phase with long-term solar a ctivity. The latitude span of the bands of torsional oscillations vari es from 0.5 R. to 1.3 R. and shows a long-term variation of about 55 y ears. The poloidal component of velocity, V-theta varies from 2 ms(-1) to 6 ms(-1). The maximum rate of the equatorial drift occurs in the p eriod between 1935 and 1955 and it develops prior to the highest maxim um activity. At the modern epoch from 1965 to 1985, V-theta does not e xceed 3 ms(-1), but now it has a tendency to increase. The bands of sl ower-than-average rotation correspond to the evolution of the magnetic activity towards the equator in the butterfly diagram.