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| Titel |
On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations |
| VerfasserIn |
V. V. Lobzin, V. V. Krasnoselskikh, K. Musatenko, T. Dudok de Wit |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 26, no. 9 ; Nr. 26, no. 9 (2008-09-23), S.2899-2910 |
| Datensatznummer |
250016236
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| Publikation (Nr.) |
 copernicus.org/angeo-26-2899-2008.pdf |
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| Zusammenfassung |
| A new method for remote sensing of the quasiperpendicular part of the bow
shock surface is presented. The method is based on analysis of high
frequency electric field fluctuations corresponding to Langmuir, upshifted,
and downshifted oscillations in the electron foreshock. Langmuir waves
usually have maximum intensity at the upstream boundary of this region. All
these waves are generated by energetic electrons accelerated by
quasiperpendicular zone of the shock front. Nonstationary behavior of the
shock, in particular due to rippling, should result in modulation of
energetic electron fluxes, thereby giving rise to variations of Langmuir
waves intensity. For upshifted and downshifted oscillations, the variations
of both intensity and central frequency can be observed. For the present
study, WHISPER measurements of electric field spectra obtained aboard
Cluster spacecraft are used to choose 48 crossings of the electron foreshock
boundary with dominating Langmuir waves and to perform for the first time a
statistical analysis of nonstationary behavior of quasiperpendicular zone of
the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy
reveals shock front nonstationarity in the frequency range 0.33 fBi<f<fBi,
where fBi is the proton gyrofrequency upstream of the
shock, and shows that the probability to observe such a nonstationarity
increases with Mach number. The profiles observed aboard different
spacecraft and the dominating frequencies of the periodicities are usually
different. Hence nonstationarity and/or rippling seem to be rather irregular
both in space and time rather than resembling a quasiregular wave
propagating on the shock surface. |
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