Voyager 1 and 2 Measurements of Galactic and Anomalous Cosmic Ray Intensities and Anisotropies in and Beyond the Heliosheath

Monday, 15 December 2014
Matthew E Hill, Johns Hopkins University, Laurel, MD, United States, Robert B Decker, Johns Hopkins Applied Physics Laboratory, Laurel, United States, Douglas C Hamilton, University of Maryland, College Park, MD, United States and Stamatios M Krimigis, Applied Physics Laboratory Johns Hopkins, Space, Laurel, MD, United States
Voyager 1 (V1) exited the nominal heliosheath in August 2012, clearly demarcated by an extreme drop in heliospheric particle intensities known as the heliocliff. Whether it entered the interstellar medium proper or some other radically different region is still subject to debate, but observationally the galactic cosmic ray (GCR) intensities and anisotropies are still varying, apparently responding to heliospheric perturbations, and the region is certainly bearing little resemblance to the expected quiescent interstellar medium. Voyager 2 (V2) continues to push towards the outer boundary of the heliosheath, being in a region heavily influenced by the interstellar interaction, as evidenced by dramatically diverted plasma flows, measuring on average greater than 60 degrees from the radial. We have studied the anomalous cosmic ray (ACR) and GCR particle behavior using V1 and V2 Low Energy Charge Particle observations, beyond the termination shock, and report the largest measured ~3% second-order GCR anisotropy at V1 after the heliocliff crossing and the order-of-magnitude variations in ACR and GCR intensities at V2 (e.g., from 2007-2012). These V2 observations are dissonant with the steady intensity profiles seen at V1 during the same period in the heliosheath and are seemingly related to the proximity to the magnetically sectored heliosheath, which arises from the increasingly compressed heliospheric current sheet (HCS) folds. We extend our earlier post-heliocliff, V1 GCR anisotropy work to the entire the heliosheath (V1 and V2) and report on the relationship between particle intensities and newly released V2 magnetometer data, particularly in regard to the HCS location.