The Rosetta Ion and Electron Sensor (IES) measurement of the development of pickup ions from comet 67P/Churyumov-Gerasimenko

• Published in: Geophysical research letters Vol. 42; no. 9; pp. 3093 - 3099
• Main Authors: Goldstein, R., Burch, J. L., Mokashi, P., Broiles, T., Mandt, K., Hanley, J., Cravens, T., Rahmati, A., Samara, M., Clark, G., Hässig, M., Webster, J. M.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 16.05.2015; John Wiley & Sons, Inc
• Subjects: Comet nuclei; Comet nucleus; Comets; Electrons; Emittance; Energy; Geophysics; Hibernation; Ions; Measurement; Nuclei; Nuclei (nuclear physics); Nucleus; Photoionization; pickup; plasma; Radiation; Rosetta mission; Sensors; Solar ultraviolet radiation; Solar wind; Solar wind ions; Spacecraft; Stellar mass; Sun; Ultraviolet radiation
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL063939

The Rosetta Ion and Electron Sensor (IES) has been measuring solar wind ions intermittently since exiting from hibernation in May 2014. On 19 August, when Rosetta was ~80 km from the comet 67P/Churyumov‐Gerasimenko, which was ~3.5 AU from the Sun, IES began to see ions at its lowest energy range, ~4–10 eV. We identify these as ions created from neutral species emitted by the comet nucleus, photoionized by solar UV radiation in the neighborhood of the Rosetta spacecraft (S/C), and attracted by the small negative potential of the S/C resulting from the population of thermal electrons. Later, IES began to see higher‐energy ions that we identify as having been picked up and accelerated by the solar wind. IES continues to measure changes in the solar wind and the development of the pickup ion structure. Key Points IES observed low‐energy ions in August 2014, at an 80 km distance from the comet