Heliosheath Thickness Implied by the Voyager Termination Shock and Heliopause Crossings

Between the termination shock and the heliopause lies the heliosheath, the region whose thickness no remote observation could measure and both Voyagers have now traversed. Voyager 1 crossed the shock at 94.0 astronomical units and the heliopause at 121.6, a sheath thickness of 27.6 astronomical units along its trajectory, while Voyager 2's crossings at 83.7 and 119.0 give 35.3 astronomical units. The mean of the two, 31.4 astronomical units, is substantially thinner relative to the shock distance than the classical gas-dynamic expectation for a strong shock with a distant boundary, and it agrees better with models in which charge exchange with interstellar neutrals drains energy and momentum from the sheath. The thicknesses are elementary differences of published crossing distances, computed and compared here with the deposited script.