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water-group ion distributions in the mid-cometosheath of comet halleyIn the mid-cometosheath of comet Halley (1-2x10^5 km from the nucleus) the center- of-mass plasma frame is approximately the bulk flow velocity of the cometary ions, and the Alfven wave speed is an appreciable fraction of the flow speed. Here, the peaks of the water-group ion distributions observed by the Giotto Ion Mass Spectrometer are at velocities consistently below the expected pickup speed. It is shown that this effect is consistent with the scattering of the new pickup ions onto a bispherical shell distribution. The model does not fit the data inside similar 1.2x10^5 km however, possibly as a result of the growing importance of collisions or the presence of other processes such as scattering on obliquely-propagating magnetosonic waves.
Document ID
20060039079
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Huddleston, D. E.
Neugebauer, M.
Goldstein, B. E.
Date Acquired
August 23, 2013
Publication Date
May 1, 1993
Publication Information
Publication: Journal of Geophysical Research
Subject Category
Geophysics
Distribution Limits
Public
Copyright
Other