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arXiv · 1505.06068

Observation of a New Type of Low Frequency Waves at Comet 67P/Churyumov-Gerasimenko

I. Richter·C. Koenders·H. -U. Auster·D. Fruehauff·C. Goetz·P. Heinisch·C. Perschke·U. Motschmann·B. Stoll·K. Altwegg·J. Burch·C. Carr·E. Cupido·A. Eriksson·P. Henri·R. Goldstein·J. -P. Lebreton·P. Mokashi·Z. Nemeth·H. Nilsson·M. Rubin·K. Szegoe·B. T. Tsurutani·C. Vallat·M. Volwerk·K. -H. Glassmeier
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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 ($\delta B/B \sim 1$), compressional magnetic field oscillations at $\sim$ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied comet-interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pick-up 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.

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I. Richter, C. Koenders, H. -U. Auster, D. Fruehauff, C. Goetz, P. Heinisch, C. Perschke, U. Motschmann, B. Stoll, K. Altwegg, J. Burch, C. Carr, E. Cupido, A. Eriksson, P. Henri, R. Goldstein, J. -P. Lebreton, P. Mokashi, Z. Nemeth, H. Nilsson, M. Rubin, K. Szegoe, B. T. Tsurutani, C. Vallat, M. Volwerk, K. -H. Glassmeier. 2015-05-22. Observation of a New Type of Low Frequency Waves at Comet 67P/Churyumov-Gerasimenko. https://doi.org/10.5194/angeo-33-1031-2015

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