First detection of a diamagnetic cavity at comet 67P/Churyumov-Gerasimenko

Goetz, C.; Koenders, C.; Richter, I.; Altwegg, Kathrin; Burch, J.; Carr, C.; Cupido, E.; Eriksson, A.; Güttler, C.; Henri, P.; Mokashi, P.; Nemeth, Z.; Nilsson, H.; Rubin, Martin; Sierks, H.; Tsurutani, B.; Vallat, C.; Volwerk, M.; Glassmeier, K.-H. (2016). First detection of a diamagnetic cavity at comet 67P/Churyumov-Gerasimenko. Astronomy and astrophysics, 588(A24), A24. EDP Sciences 10.1051/0004-6361/201527728

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Context. The Rosetta magnetometer RPC-MAG has been exploring the plasma environment of comet 67P/Churyumov-Gerasimenko since August 2014. The first months were dominated by low-frequency waves which evolved into more complex features. However, at the end of July 2015, close to perihelion, the magnetometer detected a region that did not contain any magnetic field at all. Aims. These signatures match the appearance of a diamagnetic cavity as was observed at comet 1P/Halley in 1986. The cavity here is more extended than previously predicted by models and features unusual magnetic field configurations, which need to be explained. Methods. The onboard magnetometer data were analyzed in detail and used to estimate the outgassing rate. A minimum variance analysis was used to determine boundary normals. Results. Our analysis of the data acquired by the Rosetta Plasma Consortium instrumentation confirms the existence of a diamagnetic cavity. The size is larger than predicted by simulations, however. One possible explanation are instabilities that are propagating along the cavity boundary and possibly a low magnetic pressure in the solar wind. This conclusion is supported by a change in sign of the Sun-pointing component of the magnetic field. Evidence also indicates that the cavity boundary is moving with variable velocities ranging from 230−500 m/s.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Altwegg, Kathrin and Rubin, Martin

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 620 Engineering

ISSN:

0004-6361

Publisher:

EDP Sciences

Language:

English

Submitter:

Katharina Weyeneth-Moser

Date Deposited:

18 Jul 2017 10:03

Last Modified:

23 Jul 2017 02:14

Publisher DOI:

10.1051/0004-6361/201527728

BORIS DOI:

10.7892/boris.97014

URI:

https://boris.unibe.ch/id/eprint/97014

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