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| Titel |
Relating field-aligned beams to inverted-V structures and visible auroras |
| VerfasserIn |
E. Lee, G. K. Parks, S. Y. Fu, M. Fillingim, Y. B. Cui, J. Hong, I. Dandouras, H. Rème |
| 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 ; 33, no. 10 ; Nr. 33, no. 10 (2015-10-15), S.1263-1269 |
| Datensatznummer |
250121257
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| Publikation (Nr.) |
 copernicus.org/angeo-33-1263-2015.pdf |
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| Zusammenfassung |
| The ion composition experiment on Cluster measures 3-D distributions in one
spin of the spacecraft (4 s). These distributions often measure
field-aligned ion beams (H+, He+ and O+) accelerated out of the
ionosphere. The standard model of these beams relies on a quasi-static
U-shaped potential model. The beams contain important information about the
structure and distribution of the U-shaped potential structures. For example,
a simple beam with a narrow velocity range tells us that the particles are
accelerated going through a quasi-static U-shaped potential structure
localized in space. A more complex beam with a large range of velocities
varying smoothly (a few tens of kilometers per second to
> 100 km s−1) tells us that the potential structure is extended and
distributed along the magnetic field. The Cluster experiment has now revealed
new features about the beams. Some beams are broken into many individual
structures each with their own velocity. The U-shaped potential model would
interpret the new features in terms of particles accelerated by narrow
isolated potential structures maintained over an extended region of the
magnetic field. Another interpretation is that these features arise as
Cluster traverses toward the center of a small-scale U-shaped potential
region detecting particles accelerated on different equipotential contours.
The estimate of the distance of the adjacent contours is ~ 590–610 m
at a Cluster height of ~ 3.5 RE. The observed dimensions
map to ~ 295–305 m in the ionosphere, suggesting Cluster has measured
the potential structure of an auroral arc. |
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