Galactic cosmic rays in the distant heliosphere

The small flotilla of spacecraft: Pioneers 10 and 11 and Voyagers 1 and 2 (V1 and V2) that have traveled from 1 AU to the distant heliosphere continue the quest of Victor Hess to understand the nature of this radiation that comes to us from beyond the confines of our solar system. At this time V1 and V2 are traveling deeper into the heliosheath and approaching its outer boundary - the heliopause. In the heliosheath the intensity of 2.5 - 60 MeV GCR electrons has risen significantly above detector background levels and provides an important new diagnostic tool for exploring cosmic ray transport in this previously unexplored region of space. Over the past seven months the intensity of GCR ions and electrons at V1 have remained constant after a steady, 5.5 year exponential increase whose rate varied with particle species. Is this an indication that V1 is approaching the heliopause