The geomagnetic response, as characterized by the change in daily Ap, in relation to the passage of solar magnetic sector boundaries is studied for different epochs using data for the years 1947--1978. The results derived from the whole year data indicate that the response of geomagnetic activity to a +/- boundary has remained unaltered, whereas that for a -/+ boundary has shown large variability in both form and magnitude. In the post-1962 period, when geomagnetic response for either type of boundary is similar to form, the activity associated with a +/- boundary is found to be larger than that associated with a -/+ boundary up to about 1972; from then onward this dominance is reversed. This feature is considered to be the consequence of the modulation of sector structure by north--south asymmetry in solar activity. The temporal evolution of response during equinoxes for boundaries considered favorable in the model of Russell and McPherron exhibits a 22-year modulation. This is believed to result from the modulation through the dominant polarity influence (Rosenberg and Coleman, 1969) of the basic effect related to the Russel-McPherron hypothesis.