The structure of the Heliopause

Voyager 1 has explored the solar wind-interstellar medium interaction region between the Terminal Shock and Heliopause, following the intensity distribution of the shock-accelerated anomalous component of cosmic rays in the MeV energy range. The sudden disappearance of this component at 121.7 au from the sun is discussed in terms of three models for the transition into the interstellar plasma flow. Particles trapped flowing parallel to the boundary may penetrate up to one Larmour radius. If the boundary is stationary, Voyager 1 directly samples this distance. The boundary could flap, depending on Heliosheath pressure changes and Voyager 1 then samples the extent of this motion. Finally, a turbulent boundary layer is considered in which the MeV particle distribution falls off with distance thus measuring diffusion within the layer.