Solar cycle variations of the amplitude of the solar rotation period in the geomagnetic disturbances

An investigation of the solar cycle variations of the solar rotation period is made using a method of complex demodulation of time series which estimates instantaneous amplitudes. Characteristic variations in the geomagnetic activity index agree with the Kovalenko model which describes the variations in the localization of the high-velocity streams in the solar cycle, their possible maximum rates, and their geoeffective effects (1978). It is concluded that the model explains the presence of the three minima in the solar activity geomagnetic activity index, but cannot account for the 22-year repetition of the two maxima from the decreasing part of the solar cycle.