Charge Exchange Regime in the Plasma Flow as Source of the Cometosheath and Halley's Plasma Tail

  1. Alan Johnstone
  1. Max K. Wallis

Published Online: 26 MAR 2013

DOI: 10.1029/GM061p0125

Cometary Plasma Processes

Cometary Plasma Processes

How to Cite

Wallis, M. K. (1991) Charge Exchange Regime in the Plasma Flow as Source of the Cometosheath and Halley's Plasma Tail, in Cometary Plasma Processes (ed A. Johnstone), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM061p0125

Author Information

  1. School of Mathematics, University of Wales, Cardiff CF2 4AG, Wales, U.K.

Publication History

  1. Published Online: 26 MAR 2013
  2. Published Print: 1 JAN 1991

ISBN Information

Print ISBN: 9780875900278

Online ISBN: 9781118663660

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Keywords:

  • Comets;
  • Space plasmas;
  • Astrophysics

Summary

The depletion by charge exchange of energetic cometary ions picked up in the solar wind flow into Halley's coma is calculated to coincide with the upstream extension of its cometopause, detected by the comet probes. It relates to the cometary plasma structures observed telescopically. The field-free ionospheric cavity and the cometosheath regions of Halley's plasma must in some way connect to the comet's tail. The origin of the cometosheath—envelope is argued to be due to charge—exchange cooling, this mechanism determining the source and variability of the main tail rays. The ionosphere connects to a denser tail core. The sunward part of the charge—exchange dominated cometosheath is identified on an IPD image of Halley by depletion in CO + ions. Where traversed by the comet probes, however, the cometosheath was twice as far out. Pressure—driven expansion occurs there and the sheath's main signature is a change in the flow direction.