Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
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
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 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.

Citation: Meier, P., Glassmeier, K.-H., and Motschmann, U.: Modified ion-Weibel instability as a possible source of wave activity at Comet 67P/Churyumov-Gerasimenko, Ann. Geophys., 34, 691-707, https://doi.org/10.5194/angeo-34-691-2016, 2016.
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Short summary
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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