Space Physics Seminar winter-2016

Solar Wind and Pluto Observations from the New Horizons Mission

In this presentation we describe the Solar Wind Around Pluto (SWAP) instrument on the New Horizons spacecraft. The SWAP instrument response model is based on extensive lab and inflight calibration, and this response is used to forward model the observed count rate observations in order to obtain the density, speed, and temperature. In preparation for the Pluto flyby, we used the solar wind observations to test the calibration and validate our analysis techniques to prepare for the Pluto flyby. For validation purposes, the SWAP observations were compared to both current 1 AU propagated solar wind observations, and prior Voyager 2 observations. We examined radial trends in the SWAP observations since many radial trends are well known in the inner heliosphere. In addition to the radial trends in the individual solar wind parameters, we also examined the radial trends in the solar wind speed-temperature relationship, and the periodicities present in the wind parameters. This extensive solar wind analysis not only allows us to confirm our techniques, but also provides context for the solar wind conditions during the Pluto flyby, which occurred during a solar wind compression. By comparing the Pluto flyby observations to observations from the flyby rehearsal that occurred in 2013 in the solar wind, it is clear that for more than 100 Pluto radii Pluto excludes the solar wind. We observed a change in the ratio of the primary and secondary detectors rates, and are currently performing additional laboratory calibration to determine if this is an indication of a heavy ions originating from Pluto. If so, then we observed a long Pluto tail more than 100 Pluto radii long.