Faltering Steps Into the Galaxy: The Boundary Regions of the Heliosphere

Abstract

The interaction of the heliosphere with the local interstellar medium (LISM) results in a complicated series of boundary regions. The Voyager 1 and 2 spacecraft are exploring these distant boundaries in situ, as is the Interstellar Boundary Explorer from 1 AU, which measures energetic neutral atoms created in the distant reaches of the heliosphere and LISM. Lyman-α absorption and backscatter measurements also probe the structure and physics of the interface of the heliosphere and LISM. We survey the suite of observations, the underlying theory, and the resulting models that describe the boundary regions of the solar wind and LISM.