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Properties of the singing comet waves in the 67P/Churyumov-Gerasimenko plasma environment as observed by the Rosetta mission
Univ Orleans, CNES, CNRS, UMR7328,LPC2E, Orleans, France;Univ Paris Sud, Sorbonne Univ, Ecole Polytech, UMR7648 CNRS,Lab Phys Plasmas, Paris, France.
Univ Orleans, CNES, CNRS, UMR7328,LPC2E, Orleans, France.
Univ Orleans, CNES, CNRS, UMR7328,LPC2E, Orleans, France.
Austrian Acad Sci, Space Res Inst, Graz, Austria.
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2019 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 630, article id A39Article in journal (Refereed) Published
Abstract [en]

Using in situ measurements from different instruments on board the Rosetta spacecraft, we investigate the properties of the newly discovered low-frequency oscillations, known as singing comet waves, that sometimes dominate the close plasma environment of comet 67P/Churyumov-Gerasimenko. These waves are thought to be generated by a modified ion-Weibel instability that grows due to a beam of water ions created by water molecules that outgass from the comet. We take advantage of a cometary outburst event that occurred on 2016 February 19 to probe this generation mechanism. We analyze the 3D magnetic field waveforms to infer the properties of the magnetic oscillations of the cometary ion waves. They are observed in the typical frequency range (similar to 50 mHz) before the cometary outburst, but at similar to 20 mHz during the outburst. They are also observed to be elliptically right-hand polarized and to propagate rather closely (similar to 0-50 degrees) to the background magnetic field. We also construct a density dataset with a high enough time resolution that allows us to study the plasma contribution to the ion cometary waves. The correlation between plasma and magnetic field variations associated with the waves indicates that they are mostly in phase before and during the outburst, which means that they are compressional waves. We therefore show that the measurements from multiple instruments are consistent with the modified ion-Weibel instability as the source of the singing comet wave activity. We also argue that the observed frequency of the singing comet waves could be a way to indirectly probe the strength of neutral plasma coupling in the 67P environment.

Place, publisher, year, edition, pages
2019. Vol. 630, article id A39
Keywords [en]
comets: general, comets: individual: 67P/Churyumov-Gerasimenko, plasmas, waves, methods: observational, methods: data analysis
National Category
Fusion, Plasma and Space Physics Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-395801DOI: 10.1051/0004-6361/201834876ISI: 000486989400038OAI: oai:DiVA.org:uu-395801DiVA, id: diva2:1365588
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25Bibliographically approved

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Eriksson, AndersJohansson, Fredrik
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