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Plasma fluctuations and large‐scale mixing near comet Giacobini‐Zinner
Author(s) -
Baker D. N.,
Feldman W. C.,
Gary S. P.,
McComas D. J.,
Middleditch 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/gl013i003p00271
Subject(s) - physics , comet , plasma , amplitude , electron , mixing (physics) , electron density , flow (mathematics) , spectral density , atomic physics , computational physics , astrophysics , mechanics , optics , nuclear physics , quantum mechanics , statistics , mathematics
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 ∼10 5 km of the Comet Giacobini‐Zinner nucleus. The sheath/transition region is characterized by electron temperatures of ∼4 × 10 5 K 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 ∼10 5 km from the nucleus may be operative.