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Astron. Astrophys. 325, 839-846 (1997)

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Ion emission line profiles in cometary plasma tails

H. Rauer 1, F. Roesler 2, F. Scherb 2, H.U. Schmidt 3 and R. Wegmann 3

1 Observatoire de Paris-Meudon, 5, Place Jules Janssen, F-92195 Meudon Cedex, France
2 University of Wisconsin, Madison, Wisconsin 53706, USA
3 MPI für Astrophysik, D-85748 Garching, Germany

Received 13 December 1996 / Accepted 2 April 1997

Abstract

We present a first attempt to model the profile of ion emission lines in a cometary plasma tail with the aid of a 3D-MHD model of the comet-solar wind interaction, and to compare the calculated line profiles to high-resolution measurements of the H2 O [FORMULA] doublet at 6159 Å in comet 1P/Halley on January 6, 1986. The modelled line profiles are asymmetric and show a high velocity wing originating from fast ions in the outer parts of the tail along the line-of-sight. Comparison with the measured profiles shows that such high-velocity wings are indeed observed and are needed to fully approximate the observed profiles.

We performed a quantitative analysis of the contribution of fast ions to the ion flow to examine if they are really sufficient to explain the discrepancy between measured H2 O [FORMULA] production rates and the rates expected from photoionization of water. It is found that the combined effect of fast ions and the limited field-of-view can indeed reduce the measured flux. However, the reduction seems not be sufficient to explain the whole discrepancy.

Key words: comets: general – comets: 1P/Halley

Send offprint requests to: H. Rauer

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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