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AGU: Geophysical Research Letters

 

Index Terms

  • Planetology: Comets and Small Bodies: Interactions with solar wind plasma and fields
  • Planetology: Comets and Small Bodies: Plasma and MHD instabilities
  • Space Plasma Physics: Discontinuities
  • Space Plasma Physics: Waves and instabilities

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 13, NO. 3, PP. 271-274, 1986
doi:10.1029/GL013i003p00271

Plasma fluctuations and large‐scale mixing near comet Giacobini‐Zinner

D. N. Baker

Los Alamos National Laboratory, Los Alamos, NM 87545

W. C. Feldman

Los Alamos National Laboratory, Los Alamos, NM 87545

S. P. Gary

Los Alamos National Laboratory, Los Alamos, NM 87545

D. J. McComas

Los Alamos National Laboratory, Los Alamos, NM 87545

J. Middleditch

Los Alamos National Laboratory, Los Alamos, NM 87545

Low‐pass filtered data from the ICE electron spectrometer are used to examine relationships between plasma densities, flow speeds, flow directions, and temperatures at distances within ∼105 km of the Comet Giacobini‐Zinner nucleus. The sheath/transition region is characterized by electron temperatures of ∼4 × 105K but with flow speeds and densities that commonly vary by factors of three or more. The largest amplitude density spikes often have significant flow changes associated with them, but a consistent pattern (as might accompany cometary rays, for example) is not found. Power spectral analyses in and near the sheath/transition regions show that density fluctuation levels are enhanced at all detectable frequencies from ∼0 to 21 mHz, consistent with strong density fluctuations on all measured time scales. Marginally significant power peaks are seen at periods of ∼4 min on the inbound pass and at ∼2 min on the outbound pass. Mechanisms such as amplification of convected ion pick‐up waves and cometary rays for producing the large plasma variations are discussed. It is also suggested that a Rayleigh‐Taylor driven mixing mechanism at a mass loading boundary ∼105 km from the nucleus may be operative.

Received 21 January 1986; accepted 30 January 1986; .

Citation: Baker, D. N., W. C. Feldman, S. P. Gary, D. J. McComas, and J. Middleditch (1986), Plasma fluctuations and large‐scale mixing near comet Giacobini‐Zinner, Geophys. Res. Lett., 13(3), 271–274, doi:10.1029/GL013i003p00271.

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