Annales Geophysicae
Annales Geophysicae
Annales Geophysicae
Articles | Volume 33, issue 8
Articles | Volume 33, issue 8
Ann. Geophys., 33, 1031–1036, 2015
https://doi.org/10.5194/angeo-33-1031-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 33, 1031–1036, 2015
https://doi.org/10.5194/angeo-33-1031-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Articles | Volume 33, issue 8

ANGEO Communicates 19 Aug 2015

ANGEO Communicates | 19 Aug 2015

Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko

I. Richter1, C. Koenders1, H.-U. Auster1, D. Frühauff1, C. Götz1, P. Heinisch1, C. Perschke1,2, U. Motschmann2,3, B. Stoll1, K. Altwegg4, J. Burch5, C. Carr6, E. Cupido6, A. Eriksson7, P. Henri8, R. Goldstein5, J.-P. Lebreton8, P. Mokashi5, Z. Nemeth9, H. Nilsson10, M. Rubin4, K. Szegö9, B. T. Tsurutani11, C. Vallat12, M. Volwerk13, and K.-H. Glassmeier1 I. Richter et al.
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  • 1Institut für Geophysik und extraterrestrische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
  • 2Institut für Theoretische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
  • 3German Aerospace Center (DLR), Institute of Planetary Research, Rutherfordstraße 2, 12489 Berlin, Germany
  • 4Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
  • 5Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228-0510, USA
  • 6Imperial College London, Exhibition Road, London SW7 2AZ, UK
  • 7Swedish Institute of Space Physics, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, Sweden
  • 8Laboratoire de Physique et Chimie de l'Environnement et de l'Espace, UMR 7328 CNRS – Université d'Orléans, Orléans, France
  • 9Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29–33, Budapest, Hungary
  • 10Swedish Institute of Space Physics, P.O. Box 812, 981 28 Kiruna, Sweden
  • 11Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
  • 12Rosetta Science Ground Segment, European Space Astronomy Centre, 28691 Villanueva de la Cañada, Madrid, Spain
  • 13Space Research Institute, Austrian Academy of Sciences, Schmiedlstraße 6, 8042 Graz, Austria
Received: 22 May 2015 – Revised: 14 Jul 2015 – Accepted: 17 Jul 2015 – Published: 19 Aug 2015

Abstract. We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low-activity state. Quasi-coherent, large-amplitude (δ B/B ~ 1), compressional magnetic field oscillations at ~ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied cometary interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pickup-ion-driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.

How to cite. Richter, I., Koenders, C., Auster, H.-U., Frühauff, D., Götz, C., Heinisch, P., Perschke, C., Motschmann, U., Stoll, B., Altwegg, K., Burch, J., Carr, C., Cupido, E., Eriksson, A., Henri, P., Goldstein, R., Lebreton, J.-P., Mokashi, P., Nemeth, Z., Nilsson, H., Rubin, M., Szegö, K., Tsurutani, B. T., Vallat, C., Volwerk, M., and Glassmeier, K.-H.: Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko, Ann. Geophys., 33, 1031–1036, https://doi.org/10.5194/angeo-33-1031-2015, 2015.
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Short summary
We present a first report on magnetic field measurements made in the coma of comet 67P/C-G in its low-activity state. The plasma environment is dominated by quasi-coherent, large-amplitude, compressional magnetic field oscillations around 40mHz, differing from the observations at strongly active comets where waves at the cometary ion gyro-frequencies are the main feature. We propose a cross-field current instability associated with the newborn cometary ions as a possible source mechanism.
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