The Structure of a Cometary Type I Tail: Ground-Based and Ice Observations of P/Giacobini-Zinner

  1. Thomas J. Birmingham and
  2. Alexander J. Dessler
  1. J.A. Slavin1,
  2. B.A. Goldberg1,
  3. E.J. Smith1,
  4. D.J. McComas2,
  5. S.J. Bame2,
  6. M.A. Strauss3 and
  7. H. Spinrad3

Published Online: 19 MAR 2013

DOI: 10.1029/SP027p0238

Comet Encounters

Comet Encounters

How to Cite

Slavin, J.A., Goldberg, B.A., Smith, E.J., McComas, D.J., Bame, S.J., Strauss, M.A. and Spinrad, H. (1988) The Structure of a Cometary Type I Tail: Ground-Based and Ice Observations of P/Giacobini-Zinner, in Comet Encounters (eds T. J. Birmingham and A. J. Dessler), American Geophysical Union, Washington, D.C.. doi: 10.1029/SP027p0238

Author Information

  1. 1

    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109

  2. 2

    Los Alamos National Laboratory, Los Alamos, NM 87545

  3. 3

    Department of Astronomy, University of California, Berkeley, CA 94720

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:

  • Canada-France-Hawaii Telescope (CFHT);
  • Cometary ion tails;
  • International Cometary Explorer (ICE);
  • Interplanetary magnetic field (IMF);
  • Magnetotail diameter;
  • Plasma sheet;
  • Wind-sock

Summary

The in situ magnetic field and plasma measurements from the International Cometary Explorer (ICE) Mission obtained on September 11, 1985 are compared with CCO images of P/Giacobini-Zinner (G-Z) acquired with the 3.6 m Canada-France-Hawaii Telescope (CFHT) on Mauna Kea, Hawaii and a slit spectrogram from Lick Observatory during the same period. The CFHT image at ∼3.5 hr after the ICE encounter showed a short central ion tail with a diameter of ∼3×103 km and a length of ∼2×104 km as observed in the H2O+ bandpass centered at 7025 Å. There was no distinct evidence of fine structure or ray activity. The Lick spectrogram of the H2O+ emissions taken ∼0.5 hr post-encounter with the slit perpendicular to the sun-comet line showed an ion tail with a diameter of 1.2×104 km. The ICE observations revealed a well defined 9.6×103 km diameter magnetotail composed of two magnetic lobes in pressure equilibrium with a high beta central plasma sheet. These differing measures of tail width are found to be mutually consistent if the ion emissions observed at Earth originate in a slab-shaped plasma sheet whose orientation is controlled by the direction of the interplanetary magnetic field. The results of this study also suggest that some thinning and thickening of cometary type I tails, usually attributed to plasma instabilities, may be due to changes in the angle at which the plasma sheet is viewed as IMP direction varies.