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The detectors of the UltraViolet Spectrographs (UVS) on Voyager 1/2 arerecording a background that was earlier assigned to disintegrations in the RTG.We show that it arises instead from Galactic Cosmic Rays (GCRs). We show the1992-2013 GCR flux measured by UVS on V1 and, by comparing with data from theGCR dedicated detectors, we estimate the energy range responsible for this UVSsignal, around 300 MeV, and the response of UVS to the GCR anisotropy. Afterthe abrupt jumps of May and August 2012 the count rate has been fluctuatingonly slightly around a constant value, but comparing with data from the LECPand the CRS instruments shows that those small variations are only responses toa varying anisotropy and not to a flux change. Taking advantage of thesimilarity in energy range to one of the products of the CRS instrument suite,we use the ratio between the two independent signals as a proxy for thetemporal evolution of the GCR spectral slope around the 300 MeV range. We showthat this slope has remained unchanged since Aug 2012 and find strong evidencethat it will no longer vary, implying the end of the modulation at thoseenergies and that V1 at this date is near or past the heliopause. The origin ofthis narrow and stagnating inner heliosheath is still unclear, and we discussthe potential effects of low solar wind speed episodes and subsequentself-amplified charge-exchange with interstellar neutrals, as a source ofdeceleration and collapse. We suggest that the quasi-static region encounteredby V1 may be related to such effects, triggered by the strong postsolar-maximum variability. This did not happen for V2 due to its trajectory atan angle further from the heliosphere axis and a later termination shockcrossing. The existence on the upwind side of a mixing layer formed by chargetransfer instead of a pure plasma contact discontinuity could explain variousobservations.

Galactic Cosmic Rays measured by UVS on Voyager 1 and the end of the modulation: Is the upwind heliopause a collapsed charge-exchange layer?