Journal article
An observational study of MHD wave‐induced density fluctuations upstream of the Earth's bow shock
Journal of Geophysical Research: Space Physics, Vol.93(A2), pp.845-857
02/01/1988
DOI: 10.1029/JA093iA02p00845
Abstract
A study has been made of the characteristics of MHD waves and associated density fluctuations in the Earth's foreshock. Data from two periods were analyzed. In one period the waves were circularly polarized, of 20% fractional amplitude, and propagating in a plasma with β less than one. In the second period the waves were elliptically polarized, of 50% fractional amplitude, and the plasma β was in excess of unity. The following results emerge. (1) For both periods there is a prominent feature in the density power spectrum at the same frequency as that characterizing the dominant magnetic field fluctuations. We attribute this feature to oblique wave propagation. (2) Ponderomotive effects are responsible on both days for the generation of density fluctuations on scales comparable to the wave packet sizes. There is observational evidence for modulational instability of the MHD waves on the day with β in excess of unity. (3) Evidence for a parametric decay instability was not observed, but conditions were only marginally favorable for such an observation. (4) Generation of density fluctuations by linearly polarized waves does not seem to be an important contributor to the observed density fluctuations.
Details
- Title: Subtitle
- An observational study of MHD wave‐induced density fluctuations upstream of the Earth's bow shock
- Creators
- Steven Spangler - University of IowaStephen Fuselier - Los Alamos National LaboratoryAlan Fey - University of IowaGregory Anderson - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of Geophysical Research: Space Physics, Vol.93(A2), pp.845-857
- DOI
- 10.1029/JA093iA02p00845
- ISSN
- 0148-0227
- eISSN
- 2156-2202
- Number of pages
- 13
- Language
- English
- Date published
- 02/01/1988
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199852002771
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