Observations of the onset of the new modulation cycle in 1987 using the counting rates of E>60 MeV particles at the IMP, Voyager and Pioneer spacecraft indicate that the decrease at Earth was rapid after the intensity maximum in early 1987 and was closely correlated with the increase in the average tilt of the heliospheric current sheet. Several small Forbush decreases were seen at Earth in 1987--1988 superimposed on a relatively smooth overall decrease. Similar episodic decreases were seen in Voyager 2 (V2) and Pioneer 10 (P10) following these decreases at Earth by an appropriate time delay corresponding to a propagation speed of about 400 km/s. The relative effects of these transient decreases as compared with the overall decrease was more pronounced at larger radii. By the end of 1988 the intensity had decreased by about 40% at Earth, 30% at V2 and 18% at P10. This overall decrease was accompanied by an increase in the average integral radial gradient as well as a decrease in the radial dependence of the gradient out to about 40 AU so that by the end of 1988 the gradient was ~2.0%/AU, essentially independent of radius.

V1, about 30 ¿N of the heliographic equtorial plane, observed none of the decrease seen in the equatorial plane. However, a prominent 27-day variation of peak-to-peak amplitude of ~5% was observed. As a result, the intensity at V2 in 1988 decreased below that of V1. Consequently, the latitudinal gradient present since 1985 almost completely disappeared by the end of 1988. The onset of the new solar modulation cycle seems to be related to the complete altering of the solar magnetic structure as observed on the surface of the sun. This is manifested in the heliosphere by an overall change of the average tilt of the current sheet from 9¿ to ~50¿ between 1987 and late 1988 occurring in several distinct steps which are in association with distinct changes in the magnetic structure at the Sun and with Forbush decreases observed at Earth. The relationship between the changes in the average current sheet tilt and the changes in the latitudinal and radial gradients is investigated. ¿ American Geophysical Union 1990