THE ANGULAR EXTENTS OF SOLAR INTERPLANETARY DISTURBANCES AND MODULATION OF GALACTIC COSMIC-RAYS/

From comparisons of solar activity with galactic cosmic ray (GCR) modu lation events at 1 AU and in the outer heliosphere, we argue against t he suggestion that individual solar eruptions can give rise to major c osmic ray modulation events that span the heliosphere. For the inner h eliosphere, we use a sample, covering a similar to 30-year period, of eruptive flares and confidently associated interplanetary shocks to sh ow that the following three parameters, determined at 1 AU, all decrea se with increasing longitudinal distance from the flare: probability o f detecting a shock, shock transit speed, and magnitude of any associa ted Forbush decrease (FD). In addition, we associate each of the 18 la rge (greater than or equal to 10%) FDs observed at Earth from 1958 to 1991 with one or more eruptive flares located near solar central merid ian (E47 - W31). For each of the six heliosphere-wide modulation event s that have been associated thus far by other investigators with indiv idual flares we are able to identify multiple powerful flares, with on e or more of these eruptive events generally occurring close in eclipt ic longitude to each affected spacecraft. Supporting evidence for the limited longitudinal extent of major interplanetary effects from singl e eruptions is provided by a remarkable outer heliosphere event in lat e 1989. A large shock (Delta V similar to 200 km/s) and Forbushlike de crease (18%) at Pioneer 10 at similar to 50 AU was not preceded by a c ommensurate disturbance at Voyager 1/Voyager 2/Pioneer 11 located at s imilar to 30-40 AU on the opposite side of the heliosphere. We conclud e that widespread modulation events in the outer heliosphere result fr om systems of solar/interplanetary disturbances that, only in aggregat e, encompass 360 degrees of ecliptic longitude, rather than from azimu thally symmetric shocks associated with single eruptive flares. We poi nt out that the documented preference for coronal mass ejections to oc cur at low and middle solar latitudes will naturally form the wedge-sh aped barrier proposed by Van Alien and Mihalov to account for the ''in side-out'' pattern of recovery of individual modulation events observe d at progressively greater distances in the heliosphere.