ROSINA/DFMS and IES Observations at 67P/Churyumov-Gerasimenko: Ion Neutral Chemistry in the Coma of a Weakly Outgassing Comet

Stephen A Fuselier1, Kathrin Altwegg2, Hans Balsiger2, Jean-Jacques Berthelier3, Andre Michel Bieler4, Christelle Briois5, Thomas W Broiles6, James L Burch7, Ursina Calmonte2, Michael R Combi4, Johan MSJ De Keyser8, Björn Fiethe9, Marina F Galand10, Sébastien Gasc11, Tamas I Gombosi12, Herbert Gunell8, Kenneth C Hansen4, Myrtha Hässig6, Annette Jäckel11, Ernest Kopp2, Axel Korth13, Lena Le Roy14, Urs A. Mall13, Kathleen Mandt6, Steven M Petrinec15, Henri Rème16, Martin Rubin17, Thierry Semon11, Karlheinz J Trattner18, Chia-yu Tzou11, Jack H Waite6, Erik Vigren19, Susarla Raghuram20 and Peter Wurz21, (1)Southwest Research Institute, San Antonio, TX, United States, (2)University of Bern, Bern, Switzerland, (3)CNRS-LATMOS, Paris, France, (4)University of Michigan, Ann Arbor, MI, United States, (5)Laboratoire de Physique et Chimie de l'Environnement et de l'Espace, LPC2E, Orléans Cedex 2, France, (6)Southwest Research Institute San Antonio, San Antonio, TX, United States, (7)Southwest Research Institute, San Antonio, United States, (8)Belgian Institute for Space Aeronomy, Brussels, Belgium, (9)Technical University of Braunschweig, Braunschweig, Germany, (10)Imperial College London, Department of Physics, London, United Kingdom, (11)University of Bern, Physikalisches Institut, Bern, Switzerland, (12)University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, United States, (13)Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, (14)University of Bern, Center for Space and Habitability, Bern, Switzerland, (15)Lockheed Martin Corporation, Arlington, VA, United States, (16)IRAP, Institut de Recherche en Astrophysique et Planétologie, Toulouse, France, (17)University of Bern, Physics Institute, Space Research and Planetary Sciences, Bern, Switzerland, (18)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (19)IRF Swedish Institute of Space Physics Uppsala, Uppsala, Sweden, (20)Imperial College London, London, United Kingdom, (21)University of Bern, Space Research and Planetary Sciences, Bern, Switzerland

Contact First Author: Stephen A Fuselier; stephen.fuselier@swri.org

Abstract ID#: 35480

 

English Abstract:
In August 2014, the Rosetta spacecraft encountered comet 67P/Churyumov-Gerasimenko at a distance of 3.5 AU from the Sun. Since then, the spacecraft has been observing the development of the coma around the comet. The spacecraft has a host of in situ instrumentation that includes the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument suite and the Ion and Electron Sensor (IES). Part of the ROSINA suite is an ion and neutral mass spectrometer, the Double-Focusing Mass Spectrometer (DFMS). Most often, DFMS makes high mass resolution measurements of the neutral composition of the developing coma of the comet. However, the mass spectrometer is sometimes operated in an ion mode that makes in situ measurements of key components of the ion composition of the coma. This talk focuses on these ion measurements that were made far from the Sun, when outgassing is weak and there is minimal ion-neutral chemistry in the coma. The mass ratios of newly created cometary ions are consistent with this minimal ion-neutral chemistry. Ion and electron observations of the solar wind from IES indicate that no contact surface formed upstream of the spacecraft and that newly created cometary ions are ultimately picked up by the solar wind. In this talk, the ion measurements are described and compared with ionospheric models. The implications for cometary interactions with the solar wind from 3.5 to 2.5 AU from the Sun are derived from these comparisons.
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