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| Titel |
A new technique for determining orientation and motion of a 2-D, non-planar magnetopause |
| VerfasserIn |
A. Blagau, B. Klecker, G. Paschmann, S. Haaland, O. Marghitu, M. Scholer |
| 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 ; 28, no. 3 ; Nr. 28, no. 3 (2010-03-16), S.753-778 |
| Datensatznummer |
250016801
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| Publikation (Nr.) |
 copernicus.org/angeo-28-753-2010.pdf |
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| Zusammenfassung |
For a four-point mission like Cluster, the differences in position and time
when the satellites detect the magnetopause or any other discontinuity, can
be used to infer the discontinuity local orientation, thickness and motion.
This timing technique, commonly assuming a planar geometry, offers an
independent check for various single-spacecraft techniques.
In the present paper we propose an extension of the timing method, capable of
determining in a self-consistent way the macroscopic parameters of a
two-dimensional, non-planar discontinuity. Such a configuration can be
produced by a local bulge or indentation in the magnetopause, or by a large
amplitude wave traveling on this surface, and is recognized in Cluster data
when the single spacecraft techniques provide different individual normals
contained roughly in the same plane. The model we adopted for the
magnetopause assumes a layer of constant thickness of either cylindrical or
parabolic shape, which has one or two degrees of freedom for the motion in
the plane of the individual normals. The method was further improved by
incorporating in a self-consistent way the requirement of minimum magnetic
field variance along the magnetopause normal. An additional assumption,
required in a previously proposed non-planar technique, i.e. that the
non-planarity has negligible effects on the minimum variance analysis, is
thus avoided.
We applied the method to a magnetopause transition for which the various
planar techniques provided inconsistent results. By contrast, the solutions
obtained from the different implementations of the new 2-D method were
consistent and stable, indicating a convex shape for the magnetopause. These
solutions perform better than the planar solutions from the normal magnetic
field variance perspective. The magnetopause dynamics and the presence of a
non-zero normal magnetic field component in the analyzed event are discussed. |
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