Collisional Processes in Cometary Plasmas
- Alan Johnstone
Published Online: 26 MAR 2013
Copyright 1991 by the American Geophysical Union.
Cometary Plasma Processes
How to Cite
Cravens, T. E. (2013) Collisional Processes in Cometary Plasmas, in Cometary Plasma Processes (ed A. Johnstone), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM061p0027
- Published Online: 26 MAR 2013
- Published Print: 1 JAN 1991
Print ISBN: 9780875900278
Online ISBN: 9781118663660
- Space plasmas;
The interaction of the solar wind with comets is initiated at large distances from the nucleus by the ionization of cometary neutrals. The resulting contamination of the solar wind with cometary ions massloads the solar wind flow, causing it to slow down. The plasma-comet interaction is largely collisionless at large cometocentric distances. However, collisional processes become important in the inner coma (within the cometopause). Collisional processes include charge-transfer between solar wind protons and neutrals, ion-neutral friction, electron and ion thermal cooling, and ion-neutral chemistry. For example, the magnetometer on the Giotto spacecraft observed a diamagnetic cavity near closest approach. This cavity is a consequence of the balance between an inward-directed magnetic pressure gradient force and an outward ion-neutral frictional force. Thermalization of the cometary ion distribution function by Coulomb collisions is another important process in the inner coma of an active comet.