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
Received: 11 May 2016 – Revised: 15 Jul 2016 – Accepted: 04 Aug 2016 – Published: 31 Aug 2016
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.
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, doi:10.5194/angeo-34-691-2016, 2016.