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| Titel |
Nonlinear wave-particle interaction upstream from the Earth's bow shock |
| VerfasserIn |
C. Mazelle, D. Quéau, K. Meziane |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 7, no. 3/4 ; Nr. 7, no. 3/4, S.185-190 |
| Datensatznummer |
250004256
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| Publikation (Nr.) |
 copernicus.org/npg-7-185-2000.pdf |
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| Zusammenfassung |
| Well-defined ring-like backstreaming ion
distributions have been recently reported from observations made by the
3DP/PESA-High analyzer onboard the WIND spacecraft in the Earth's foreshock at
large distances from the bow shock, which suggests a local production mechanism.
The maximum phase space density for these distributions remains localized at a
nearly constant pitch-angle value for a large number of gyroperiods while the
shape of the distribution remains very steady. These distributions are also
observed in association with quasi-monochromatic low frequency (~ 50 mHz) waves
with substantial amplitude (δB/B>0.2). The analysis of the magnetic
field data has shown that the waves are propagating parallel to the background
field in the right-hand mode. Parallel ion beams are also often observed in the
same region before the observation of both the ring-like distributions and the
waves. The waves appear in cyclotron resonance with the ion parallel beams. We
investigate first the possibility that the ion beams could provide the free
energy source for driving an ion/ion instability responsible for the ULF wave
occurrence. For that, we solve the wave dispersion relation with the observed
parameters. Second, we show that the ring-like distributions could then be
produced by a coherent nonlinear wave-particle interaction. It tends to trap the
ions into narrow cells in velocity space centered on a well-defined pitch-angle,
directly related to the saturation wave amplitude in the analytical theory. The
theoretical predictions are in good quantitative agreement with the
observations |
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