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Astron. Astrophys. 325, 839-846

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Ion emission line profiles in cometary plasma tails

H. Rauer1, F. Roesler2, F. Scherb2, H.U. Schmidt3, and R. Wegmann3

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

Received 13 December 1996 / Accepted 2 April 1997


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 H2O+ doublet at 6159Å 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 H2O+ 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

© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 28, 1998