Voyager’s Observations in the Vicinity of the Heliopause

Abstract

This work analyzes Voyager 2 observations on November 2018 and compares them with Voyager 1 data at the vicinity of the heliopause in July-August 2012. We describe the plasma and cosmic-ray variations at the radial distance of ≈ 1 astronomical unit (AU) from the heliopause. We use a simple convection-diffusion cosmic-ray modulation model to qualitatively explain the particle observations. We found a thin layer, with a thickness of ≈ 0.04 AU where the radial component of the solar wind speed vanished, the galactic cosmic ray intensity rapidly increased to reach its heliosphere boundary level, and low-energy heliospheric ion intensity drooped. We called this layer the “skin of the heliosphere”. Plasma data suggest that Voyager 2 crossed the heliopause on November 5, 2018, at the radial distance of 119.03 AU. We apply our analysis to Voyager 1 observations and conclude that similar behavior in solar wind speed could qualitatively explain the GCR counting rate and that the “skin of the heliosphere” maybe a global characteristic along the heliopause.