An Explanation for the Recent Voyager 1 Observations

A model is presented that can account for the recent Voyager 1 observations: (1) beyond ~113 AU from the Sun, the anisotropy of low-energy ions becomes very small in all directions, which has been interpreted as indicating that the solar wind flow speed has decreased to near zero; (2) at ~120 AU, anomalous cosmic rays (ACRs) are accelerated to their highest energies; (3) at ~122 AU, there is a precipitous decrease both in ACRs and in termination shock particles (TSPs) that are convected downstream from the termination shock; and (4) coincident with the decrease in ACRs and TSPs there is an commensurate increase in the magnetic field, but no change in the magnetic field direction. In this presentation, the low-energy anisotropy observations are interpreted as implying, not that the solar wind flow speed has decreased to near zero, but rather that the solar wind flow is closely aligned with the magnetic field direction, which is observed to be in the azimuthal direction. A simple model for the heliosheath is then constructed, based on the anisotropy observations and the observational evidence that the dominant pressure is contained in pickup ions, TSP, and ACRs. The model predicts that there are jets of supersonic and super-Alfvénic solar wind flowing along the flanks of the heliosheath, stretching and opening the heliosheath magnetic field into the interstellar medium. TSPs and ACRs that are accelerated in the nose region can easily escape along the magnetic field in the open region of the heliosheath, resulting in the precipitous decrease in the intensity of TSPs and ACRs, and offering an explanation for other Voyager 1 and IBEX observations.