Voyager I Observations of Unusual Variations of Galactic Cosmic Rays in the Distant Heliosheath

On 2012.35 at 120.5 AU, the Voyager CRS experiment (E. C. Stone, PI) observed a rapid increase in Galactic Cosmic Ray (GCR) ions and electrons that reached a quasi-plateau level lasting for some 76 days. There then began a second increase on 2012.57 that is still evolving. For the first increase, the temporal profile was essentially the same for all components but there was an inverse rigidity dependence of the magnitude of the increase which extended up to 600 MeV/n He. The 10 MeV electrons increased by ~28%. The low energy electrons in this plateau region also show a significant ~6 day temporal variation. Both the Voyager 1 (V1) and Voyager 2 (V2) GCR He spectra are in excellent agreement with the predictions of Webber and Higbie for the interstellar spectrum. These increases represent a strong change from the relatively smooth exponential increase of GCR ions from 2006.25-2011.7. Over this period the 10 MeV electrons experienced two rapid increases which were slightly smaller in amplitude than the May 2012 increase. Around 2011.7 the time-history of all GCR ions and electrons become essentially flat over the ensuing 8 months. This marked change in the behavior of GCRs along with the simultaneous decrease of ACRs (as reported in an accompanying paper), indicate that V1 has entered a new modulation region closer to the heliopause.