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Whistler waves observed upstream from collisionless shocks

1974; American Geophysical Union; Volume: 79; Issue: 10 Linguagem: Inglês

10.1029/ja079i010p01368

2156-2202

D. H. Fairfield,

Earthquake Detection and Analysis

Journal of Geophysical Research (1896-1977)Volume 79, Issue 10 p. 1368-1378 Whistler waves observed upstream from collisionless shocks D. H. Fairfield, D. H. FairfieldSearch for more papers by this author D. H. Fairfield, D. H. FairfieldSearch for more papers by this author First published: 1 April 1974 https://doi.org/10.1029/JA079i010p01368Citations: 172AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract Waves in the frequency range 0.5–4. Hz have been studied in the region upstream of the earth's bow shock with data from the flux-gate magnetic field experiment on Imp 6. Such waves are invariably detected adjacent to the shock, persisting upstream for intervals often less than a minute but occasionally of the order of many hours. Analysis of 150 examples of these waves (ΔB/B ≃0.2) during a 3-month interval indicates that propagation directions generally make angles of between 20° and 40° with the field direction. The waves as measured in the spacecraft frame of reference are either left- or right-hand-polarized with respect to the average field direction. The left-handed waves generally have lower frequencies than the right-handed waves, and the left-handed frequencies never exceed 2.5 Hz. The measured sense of polarization is found to depend on the propagation direction (or alternatively, the field direction) relative to the solar wind direction. Propagation-solar wind angles greater than approximately 40° (or field angles greater than 55°) correspond to right-hand polarization, and smaller angles correspond to left-hand polarization. It is concluded that the observed waves are right-handed waves in the plasma frame of reference with wavelengths of approximately 100 km propagating upstream in the whistler mode. Doppler-shifting reduces the observed frequencies in the spacecraft frame and reverses the observed polarization for those waves propagating more directly upstream. Similar waves are seen ahead of some interplanetary shocks. References Barnes, A., Theory of generation of bow-shock-associated hydromagnetic waves in the upstream interplanetary medium, Cosmic Electrodynamics, 1, 90–114, 1970. Bendat, J. S., A. G. Piersol, Measurement and Analysis of Random Data, 31–33, John Wiley, New York, 1966. Chao, J. K., N. F. Ness, W. C. Feldman, S. J. Bame, Perpendicular shocks in the solar wind (abstract), Eos Trans. 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Citing Literature Volume79, Issue10Space Physics1 April 1974Pages 1368-1378 ReferencesRelatedInformation