Recent Measurement of Energetic Particles from Voyagers 1 and 2

We review recent measurements of energetic particles made at Voyager 2 (at 116 AU, S32 deg) in the heliosheath and at Voyager 1 (at 140 AU, N35 deg) in the local interstellar medium. Voyager 2 is 31 AU beyond its termination shock crossing (84.4 AU in August 2007), showing that the heliosheath at Voyager 2 is at least 3-4 AU thicker than that traversed by Voyager 1. In the 2017 data at Voyager 2, intensities of heliosheath ions >30 keV and electrons >20 keV have levelled off, with the ions reaching values comparable to those in 2011, following a four-year step-like recovery from minima reached in early 2013. In addition, during 2014-17, variations of the lowest energy ion intensities with scales of order several months or less tend to correlate with similar variations in the solar wind density. This similarity of relatively short-term temporal variations between the thermal and suprathermal ions was not seen in the earlier heliosheath data from Voyager 2. Voyager 1 is now about 18 AU upstream of the heliopause nose. Intensities of low-energy ions and electrons and of anomalous cosmic rays, all of which were routinely measured in the heliosheath, remain at background levels at Voyager 1 through July 2017. Angular distributions of galactic cosmic ray protons >211 MeV continue to depart from isotropy, being characterized instead by broad (0.3-0.8 year) episodes of steady intensity depletions of protons gyrating nearly perpendicular to the magnetic field. Although data in the first half of 2017 continue to show departures from isotropy, the anisotropy amplitudes are generally small, comparable to periods of quasi-isotropy measured during six-month periods in 2013-14 and in 2014-15.