IBEX Observations provide strong Evidence that Voyager 1 is still in the Heliosheath

Abstract

After plasma wave measurements by Voyager 1 (V1) revealed a surprisingly high value for the plasma electron density, a value close to that expected in the local interstellar medium, all principal investigators of the Voyager mission currently exploring the heliosheath suddenly reversed their position on the location of V1. They concluded unanimously, and NASA announced that V1 has crossed the heliopause and is now in local interstellar space. We have disputed this conclusion, pointing out that to account for all the V1 observations, particularly of the magnetic field direction together with the density, it is necessary to conclude that the higher densities observed by V1 are due to compressed solar wind. In this paper we show that our model for the nose region of the heliosheath can account in detail for the spectral shapes and intensities of Energetic Neutral Hydrogen (ENH) observed by the Interstellar Boundary Explorer (IBEX) looking in the directions of V1 and Voyager 2 (V2). A key feature of our model is the existence of a region, the hot heliosheath, where the outward-moving solar wind is gradually compressed and thus heated, followed by a region, the cold heliosheath, where the solar wind is still compressed but now cold. It is the existence of this cold heliosheath, the region of cold but high-density solar wind, which provides a unique and simple explanation for the low-energy IBEX ENH differential intensities. Finally, since this cold heliosheath is the region where V1 must now reside, the low-energy IBEX observations provide strong evidence that V1 is still in the heliosphere.