P31E-2096
High-energy pickup ions measured at Comet 67P/Churyumov-Gerasimenko by the Rosetta Ion and Electron Sensor (IES)
Wednesday, 16 December 2015
Poster Hall (Moscone South)
Raymond Goldstein1, James L Burch1, Prachet Mokashi2, Jerry Goldstein1, Thomas W Broiles1, Kathleen Mandt1 and Hans Nilsson3, (1)Southwest Research Institute, San Antonio, TX, United States, (2)Southwest Research Institute San Antonio, San Antonio, TX, United States, (3)IRF Swedish Institute of Space Physics Kiruna, Kiruna, Sweden
Abstract:
During April 2015, while the Rosetta spacecraft was ~100 km from comet Churyumov-Gerasimenko (which was ~1.8 AU from the Sun), the IES instrument on board the Rosetta spacecraft observed ions of energy near 17 keV, its highest capability, flowing in a broad angular distribution ~45° to the anti-sunward direction. We suggest that these are ions created far from the comet, picked up by the solar wind and carried back toward the comet. Their high energy suggests that these are ions resulting from a combination of photo-ionization and photo-dissociation of the neutral water molecules from the nucleus (i.e. O+, OH+, H2O+, and possibly H3O+). Such high energy pickup ions were seen during the Giotto flyby of comet Halley. The IES data also show ~keV level ions from the direction of the comet, that we postulate are anti-sunward ions (solar wind and/or pickup ions) that have been reflected from the comet nucleus and moving back in the solar direction. We will present results of analysis of the IES measurements supporting these conclusions.
