Kelvin-Helmholtz instabilities at the magnetic cavity boundary of comet 67P/Churyumov-Gerasimenko

Rubin, Martin; Hansen, K. C.; Combi, M. R.; Daldorff, L. K. S.; Gombosi, T. I.; Tenishev, V. M. (2012). Kelvin-Helmholtz instabilities at the magnetic cavity boundary of comet 67P/Churyumov-Gerasimenko. Journal of geophysical research, 117(A6), n/a-n/a. American Geophysical Union 10.1029/2011JA017300

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We investigate the plasma environment of comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's Rosetta mission. Rosetta will rendezvous with the comet in 2014 at almost 3.5 AU and follow it all the way to and past perihelion at 1.3 AU. During its journey towards the inner solar system the comet's environment will significantly change. The interaction of the solar wind with a well developed neutral coma leads to the formation of an upstream bow shock and, closer to the comet, the inner shock separating the solar wind, with cometary pick-up ions mass-loaded, from the inner cometary ions which are dragged outward through abundant collisions and charge exchange with the expanding neutral gas. As a consequence the interplanetary magnetic field is prevented from penetrating the innermost region of the comet, the so-called magnetic cavity. We use our magnetohydrodynamics model BATSRUS (Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme) to simulate the solar wind - comet interaction. The model includes photoionization, ion-electron recombination, and charge exchange. Under certain conditions our model predicts an unstable plasma flow at the inner shock. We show that the plasma shear flow around the magnetic cavity can lead to Kelvin-Helmholtz instabilities. We investigate the onset of this phenomenon with change of heliocentric distance and furthermore show that a previously stable magnetic cavity boundary can become unstable when the neutral gas is predominately released from the dayside of the comet.

Item Type:

Journal Article (Original Article)

Division/Institute:

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

UniBE Contributor:

Rubin, Martin

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering

ISSN:

0148-0227

Publisher:

American Geophysical Union

Language:

English

Submitter:

Martin Rubin

Date Deposited:

04 May 2016 15:56

Last Modified:

11 Sep 2017 13:03

Publisher DOI:

10.1029/2011JA017300

BORIS DOI:

10.7892/boris.74098

URI:

https://boris.unibe.ch/id/eprint/74098

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