Hydromagnetic Waves and Instabilities Associated with Cometary Ion Pickup: Ice Observations
- Thomas J. Birmingham and
- Alexander J. Dessler
Published Online: 19 MAR 2013
Copyright 1988 by the American Geophysical Union.
How to Cite
Tsurutani, B. T. and Smith, E. J. (1988) Hydromagnetic Waves and Instabilities Associated with Cometary Ion Pickup: Ice Observations, in Comet Encounters (eds T. J. Birmingham and A. J. Dessler), American Geophysical Union, Washington, D.C.. doi: 10.1029/SP027p0081
- Published Online: 19 MAR 2013
- Published Print: 1 JAN 1988
Print ISBN: 9780875902395
Online ISBN: 9781118668757
- Cometary ion;
- Hydromagnetic waves;
- Wave packets
The hydromagnetic turbulence surrounding comet Giacobini-Zinner is characterized by two dominent components: large amplitude, linearly polarized waves with periods near 102 s and circularly polarized wave packets with periods near 3 s. The latter appear in association with variations in field magnitude produced by the long period waves. A third, commonly observed feature is identified, consisting of a partial rotation of the magnetic field (a hooklike structure) which also appears to be triggered by the long period waves. The possibility that the long period waves are generated by the pickup of freshly ionized cometary neutrals has been investigated. A resonant instability identified by Wu and Davidson (1972) appears able to account for the long period waves in terms of the pickup of cometary ions of the water group. Application of the theory also indicates that the growth rate of proton cyclotron waves, as a consequence of hydrogen ion pickup, is somewhat lower, due to both higher neutral velocities and longer ionization times. Several significant features of the wave packets and hooks are presently unexplained and will require further study.