A Theory for Low-Frequency Waves Observed at Comet Giacobini-Zinner

  1. Thomas J. Birmingham and
  2. Alexander J. Dessler
  1. M.L. Goldstein1 and
  2. H.K. Wong2

Published Online: 19 MAR 2013

DOI: 10.1029/SP027p0111

Comet Encounters

Comet Encounters

How to Cite

Goldstein, M.L. and Wong, H.K. (1988) A Theory for Low-Frequency Waves Observed at Comet Giacobini-Zinner, in Comet Encounters (eds T. J. Birmingham and A. J. Dessler), American Geophysical Union, Washington, D.C.. doi: 10.1029/SP027p0111

Author Information

  1. 1

    Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland

  2. 2

    Department of Space Sciences, Southwest Research Institute, San Antonio, Texas

Publication History

  1. Published Online: 19 MAR 2013
  2. Published Print: 1 JAN 1988

ISBN Information

Print ISBN: 9780875902395

Online ISBN: 9781118668757

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Keywords:

  • Beam-driven instabilities;
  • Comet Giacobini-Zinner;
  • High-frequency waves;
  • International Cometary Explorer (ICE);
  • Low-frequency waves;
  • Solar wind velocity

Summary

As the ICE spacecraft approached comet Giacobini-Zinner, low-frequency waves in two frequency ranges were observed in the magnetic field data. We show that, under certain conditions, a gyrating beam of water group ions is capable of generating electromagnetic waves with periods near 100 s (in the spacecraft frame of reference) and shorter-period whistler branch waves with periods near 3 s. The 100-s wave can arise from either a nonresonant firehose instability or a resonant beam driven instability so long as the angle between the directions of the local magnetic field and solar wind velocity is less than 90°. Whenever that angle exceeds about 30°, the gyrating ring distribution formed by newly ionized water is also unstable to the generation of whistler waves with 3-s periods.