An MHD Model of Cometary Plasma and Comparison with Observations

  1. Alan Johnstone
  1. H.U. Schmidt and
  2. R. Wegmann

Published Online: 26 MAR 2013

DOI: 10.1029/GM061p0049

Cometary Plasma Processes

Cometary Plasma Processes

How to Cite

Schmidt, H.U. and Wegmann, R. (1991) An MHD Model of Cometary Plasma and Comparison with Observations, in Cometary Plasma Processes (ed A. Johnstone), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM061p0049

Author Information

  1. Max-Planck-Institut für Astrophysik, Karl-Schwarzschildstr.1, D-8046 Garching, FRG

Publication History

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

ISBN Information

Print ISBN: 9780875900278

Online ISBN: 9781118663660



  • Comets;
  • Space plasmas;
  • Astrophysics


Cometary plasma flow was sampled by spacecraft along inclined trajectories through comets Giacobini-Zinner and Halley. The interpretation of these observations needs extensive modeling of the whole comet. Here we review some global simulations of cometary plasma flow based mainly on MHD. We discuss features from the first deceleration of the solar wind outside the bow shock to the radial expansion of the purely cometary plasma inside the contact surface and to the cometary tail downwind. For the interaction of solar UV, solar wind, and cometary matter many processes must be considered: In the outermost regions mainly photoionisation of neutrals as well as pitch angle anisotropy and scattering. Towards the nucleus collisional processes become important: charge exchange, ionisation and dissociation by electron impact, possibly critical velocity effects, recombination processes, and momentum exchange with the counterstreaming neutrals. Chemical kinetics of plasma and neutral gases evaporating from nucleus and dust needs accounting. Lorentz forces necessitate 3D simulation of the magnetic pile up.