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| Titel |
A statistical study of the upstream intermediate ion boundary in the Earth's foreshock |
| VerfasserIn |
K. Meziane, C. D'Uston |
| 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 ; 16, no. 2 ; Nr. 16, no. 2, S.125-133 |
| Datensatznummer |
250013148
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| Publikation (Nr.) |
 copernicus.org/angeo-16-125-1998.pdf |
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| Zusammenfassung |
A statistical investigation of the location
of onset of intermediate and gyrating ion populations in the Earth's foreshock
is presented based on Fixed Voltage Analyzer data from ISEE 1. This study
reveals the existence of a spatial boundary for intermediate and gyrating ion
populations that coincides with the reported ULF wave boundary. This boundary
position in the Earth's foreshock depends strongly upon the magnetic cone angle
θBX and appears well defined for relatively large
cone angles, though not for small cone angles. As reported in a previous study
of the ULF wave boundary, the position of the intermediate-gyrating ion boundary
is not compatible with a fixed growth rate of the waves resulting from the
interaction between a uniform beam and the ambient plasma. The present work
examines the momentum associated with protons which travel along this boundary,
and we show that the variation of the boundary position (or equivalently, the
associated particle momentum) with the cone angle is related to classical
acceleration mechanisms at the bow shock surface. The same functional behavior
as a function of the cone angle is obtained for the momentum predicted by an
acceleration model and for the particle momentum associated with the boundary.
However, the model predicts systematically larger values of the momentum than
the observation related values by a constant amount; we suggest that this
difference may be due to some momentum exchange between the incident solar-wind
population and the backstreaming particles through a wave-particle interaction
resulting from a beam plasma instability.
Key words. Intermediate ion boundary · Statistical
investigation · Earth's foreshock · ISEE 1 spacecraft |
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