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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 34, issue 9
Ann. Geophys., 34, 691–707, 2016
https://doi.org/10.5194/angeo-34-691-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 34, 691–707, 2016
https://doi.org/10.5194/angeo-34-691-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 31 Aug 2016

Regular paper | 31 Aug 2016

Modified ion-Weibel instability as a possible source of wave activity at Comet 67P/Churyumov-Gerasimenko

Patrick Meier1,2, Karl-Heinz Glassmeier1,3, and Uwe Motschmann2,4 Patrick Meier et al.
  • 1Institut für Geophysik und extraterrestrische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
  • 2Institut für Theoretische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
  • 3Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
  • 4German Aerospace Center (DLR), Institute of Planetary Research, Rutherfordstr. 2, 12489 Berlin, Germany

Abstract. We analytically discuss wave excitation in a homogeneous three component plasma consisting of solar wind protons, electrons and a beam of cometary water ions applied to the plasma environment of comet 67P/Churyumov-Gerasimenko. The resulting dispersion relations are studied in a solar wind rest frame, where a cometary current is solely generated by the water ion beam, and a cometary rest frame representing the rest frame of the Rosetta spacecraft. A modified ion-Weibel instability is excited by the cometary current and predominantly grows perpendicular to this current. The corresponding water ion mode is connected to a frequency of about 40 mHz in agreement with wave measurements of Rosetta's magnetometer in the cometary rest frame. Furthermore, the superposition of the strongest growing waves result in a fan-like phase structure close to the comet.

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A new type of wave has been detected by the magnetometer of the Rosetta spacecraft close to comet P67/Churyumov-Gerasimenko. We provide the analytical model of this wave excitation from linear perturbation theory. A modified ion-Weibel instability is identified as source of this wave excited by a cometary current. The waves predominantly grow perpendicular to this current. A fan-like phase structure results from superposing the strongest growing waves in a cometary rest frame.
A new type of wave has been detected by the magnetometer of the Rosetta spacecraft close to...
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