Implications of the Voyager 1 and 2 Particle and Field Observations around their respective Heliopause Crossings

Abstract

The numerous contrasts between the Voyager 1 particle and field observations around its heliopause crossing in 2012 and the corresponding observations by Voyager 2 in late 2018 and the beginning of 2019 are consistent with understanding the heliopause itself as the separator between the solar system magnetic field and the interstellar medium magnetic field, at a location that varies in response both to short-term effects of plasma instabilities and longer-term bulk motions of the heliosheath. Plasma flows in the respective regions provide a framework for explaining the observed decreases with heliopause distance of the count rates of both solar system solar and anomalous cosmic rays diffusing outward from the heliopause and galactic cosmic rays diffusing inward. Formation of excited hydrogen atoms by chargeexchange collisions in interstellar plasma displaced and accelerated (as described in the discussion of solar system cosmic rays) by the motion of the heliosphere provides a mechanism for producing recently recognized anomalous Lyman alpha emissions around the front of the heliosphere. We discuss the consequent possibility of previously unobserved Lyman alpha emissions associated with shock propagation in the local interstellar medium.