Diamagnetic region(s): structure of the unmagnetized plasma around Comet 67P/CG

Henri, P.; Vallières, X.; Hajra, R.; Goetz, C.; Richter, I.; Glassmeier, K.-H.; Galand, M.; Rubin, Martin; Eriksson, A. I.; Nemeth, Z.; Vigren, E.; Beth, A.; Burch, J.L.; Carr, C.; Nilsson, H.; Tsurutani, B.; Wattieaux, G. (2017). Diamagnetic region(s): structure of the unmagnetized plasma around Comet 67P/CG. Monthly notices of the Royal Astronomical Society, 469(Suppl_2), S372-S379. Oxford University Press 10.1093/mnras/stx1540

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The ESA’s comet chaser Rosetta has monitored the evolution of the ionized atmosphere of comet 67P/Churyumov–Gerasimenko (67P/CG) and its interaction with the solar wind, during more than 2 yr. Around perihelion, while the cometary outgassing rate was highest, Rosetta crossed hundreds of unmagnetized regions, but did not seem to have crossed a large-scalen diamagnetic cavity as anticipated. Using in situ Rosetta observations, we characterize the structure of the unmagnetized plasma found around comet 67P/CG. Plasma density measurements from RPC-MIP are analysed in the unmagnetized regions identified with RPC-MAG. The plasma observations are discussed in the context of the cometary escaping neutral atmosphere, observed by ROSINA/COPS. The plasma density in the different diamagnetic regions crossed by Rosetta ranges from ~100 to ~1500 cm⁻³. They exhibit a remarkably systematic behaviour that essentially depends on the comet activity and the cometary ionosphere expansion. An effective total ionization frequency is obtained from in situ observations during the high outgassing activity phase of comet 67P/CG. Although several diamagnetic regions have been crossed over a large range of distances to the comet nucleus (from 50 to 400 km) and to the Sun (1.25–2.4 au), in situ observations give strong evidence for a single diamagnetic region, located close to the electron exobase. Moreover, the observations are consistent with an unstable contact surface that can locally extend up to about 10 times the electron exobase.

Item Type:

Journal Article (Original Article)

Division/Institute:

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

UniBE Contributor:

Rubin, Martin

Subjects:

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

ISSN:

0035-8711

Publisher:

Oxford University Press

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

15 Nov 2017 11:06

Last Modified:

15 Nov 2017 11:06

Publisher DOI:

10.1093/mnras/stx1540

BORIS DOI:

10.7892/boris.105810

URI:

https://boris.unibe.ch/id/eprint/105810

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