Pluto's interaction with the solar wind

This study provides the first observations of Plutogenic ions and their unique interaction with the solar wind. We find 20% solar wind slowing that maps to a point only 4.5 R-P upstream of Pluto and a bow shock most likely produced by comet-like mass loading. The Pluto obstacle is a region of dense heavy ions bounded by a Plutopause where the solar wind is largely excluded and which extends back >100 R-P into a heavy ion tail. The upstream standoff distance is at only 2.5 R-P. The heavy ion tail contains considerable structure, may still be partially threaded by the interplanetary magnetic field (IMF), and is surrounded by a light ion sheath. The heavy ions (presumably CH4+) have average speed, density, and temperature of 90kms(-1), 0.009cm(-3), and 7x10(5)K, with significant variability, slightly increasing speed/temperature with distance, and are N-S asymmetric. Density and temperature are roughly anticorrelated yielding a pressure 2x10(-2)pPa, roughly in balance with the interstellar pickup ions at 33AU. We set an upper bound of <30nT surface field at Pluto and argue that the obstacle is largely produced by atmospheric thermal pressure like Venus and Mars; we also show that the loss rate down the tail (5x10(23)s(-1)) is only 1% of the expected total CH4 loss rate from Pluto. Finally, we observe a burst of heavy ions upstream from the bow shock as they are becoming picked up and tentatively identify an IMF outward sector at the time of the NH flyby.