Influence of Solar Disturbances on Galactic Cosmic Rays in the Solar Wind, Heliosheath, and Local Interstellar Medium: Advanced Composition Explorer, New Horizons, and Voyager Observations

We augmented the heliospheric network of cosmic ray monitors using penetrating radiation measurements from the New Horizons (NH) Pluto Energetic Particle Spectrometer Science Investigation to obtain intensities of ≳65 MeV particles. The new high-energy capability, corresponding predominantly to galactic cosmic rays (GCRs), provides the critical observational links between the Sun and Voyager 2 and Voyager 1 (V2 and V1) while in the heliosheath and local interstellar medium (LISM), respectively. We report on GCRs observed at NH during 2012-2017 and corresponding GCR, energetic particle, and plasma measurements observed during comparable periods at the Advanced Composition Explorer (ACE), NH, V2, and V1. These observations allow us to track long-term solar cycle variations and short-term Forbush decreases across the heliosphere and into interstellar space and, therefore, examine the interaction between the heliosphere and the LISM, where long V1 anisotropy episodes have been observed. To investigate these episodes and the unexplained lagging of associated in situ shock features at V1, propagating disturbances (from ACE, NH, and V2 data) were compared with V1 data. We conclude that the region where the LISM magnetic field lines drape over the heliopause is critical for communicating solar disturbance signals upstream of the heliosheath to V1. We propose that the physical process responsible for the suppressed intensities at ~90˚ pitch angles (the cause of the anisotropies) relies on GCRs escaping from the single compression in the draping region not on GCRs trapped between two compressions.