3 VIEWS OF 2 GIANT STREAMS - ALIGNED OBSERVATIONS AT 1 AU, 4.6 AU, AND 5.9 AU

A close radial alignment of the IMP and Pioneers 10 and 11 spacecraft in 1974 allows a nearly unambiguous , empirical study of the radial ev olution of the interaction regions of two contrasting weak and strong, giant streams. The study confirms the main aspects of the standard mo del of corotating interaction regions: an expanding and strengthening pair of forward-reverse shocks sandwich a stream interface. It adds th e following concepts: stream group speed--the speed at the stream inte rface tends to remain constant with distance; corotating stream comple xes--interaction regions can include features like noncompressive dens ity enhancements and streamer belts; secondary interfaces--a possible precursor to the reverse shock; and emerging stream interfaces--one em erged between 1 AU and 4.6 AU. The study uses the conservation specifi c entropy to correlate features between spacecraft.