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Hydromagnetic waves and instabilities associated with cometary ion pickup: ICE observations
Author(s) -
Tsurutani Bruce T.,
Smith Edward J.
Publication year - 1986
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl013i003p00263
Subject(s) - physics , ionization , ion , instability , astrophysics , wave packet , magnetic field , amplitude , atomic physics , pickup , proton , wave propagation , electromagnetic radiation , computational physics , geophysics , optics , mechanics , nuclear physics , quantum mechanics , artificial intelligence , computer science , image (mathematics)
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 hook‐like 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.