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| Titel |
Cluster observations of the high-latitude magnetopause and cusp: initial results from the CIS ion instruments |
| VerfasserIn |
J. M. Bosqued, T. D. Phan, I. Dandouras, C. P. Escoubet, H. Rème, A. Balogh, M. W. Dunlop, D. Alcaydé, E. Amata, M.-B. Bavassano-Cattaneo, R. Bruno, C. Carlson, A. M. DiLellis, L. Eliasson, V. Formisano, L. M. Kistler, B. Klecker, A. Korth, H. Kucharek, R. Lundin, M. McCarthy, J. P. McFadden, E. Möbius, G. K. Parks, J.-A. Sauvaud |
| 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 ; 19, no. 10/12 ; Nr. 19, no. 10/12, S.1545-1566 |
| Datensatznummer |
250014134
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| Publikation (Nr.) |
 copernicus.org/angeo-19-1545-2001.pdf |
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| Zusammenfassung |
Launched on an elliptical
high inclination orbit (apogee: 19.6 RE) since January 2001
the Cluster satellites have been conducting the first detailed
three-dimensional studies of the high-latitude dayside magnetosphere, including
the exterior cusp, neighbouring boundary layers and magnetopause regions.
Cluster satellites carry the CIS ion spectrometers that provide high-precision,
3D distributions of low-energy (<35 keV/e) ions every 4 s. This paper
presents the first two observations of the cusp and/or magnetopause behaviour
made under different interplanetary magnetic field (IMF) conditions. Flow
directions, 3D distribution functions, density profiles and ion composition
profiles are analyzed to demonstrate the high variability of high-latitude
regions. In the first crossing analyzed (26 January 2001, dusk side, IMF-BZ
< 0), multiple, isolated boundary layer, magnetopause and magnetosheath
encounters clearly occurred on a quasi-steady basis for ~ 2 hours. CIS ion
instruments show systematic accelerated flows in the current layer and adjacent
boundary layers on the Earthward side of the magnetopause. Multi-point analysis
of the magnetopause, combining magnetic and plasma data from the four Cluster
spacecraft, demonstrates that oscillatory outward-inward motions occur with a
normal speed of the order of ± 40 km/s; the thickness of the high-latitude
current layer is evaluated to be of the order of 900–1000 km. Alfvénic
accelerated flows and D-shaped distributions are convincing signatures of a
magnetic reconnection occurring equatorward of the Cluster satellites.
Moreover, the internal magnetic and plasma structure of a flux transfer event
(FTE) is analyzed in detail; its size along the magnetopause surface is ~ 12
000 km and it convects with a velocity of ~ 200 km/s. The second event analyzed
(2 February 2001) corresponds to the first Cluster pass within the cusp when
the IMF-BZ component was northward directed. The analysis of relevant CIS
plasma data shows temporal cusp structures displaying a reverse energy-latitude
"saw tooth" dispersion, typical for a bursty reconnection between the
IMF and the lobe field lines. The observation of D-shaped distributions
indicates that the Cluster satellites were located just a few RE
from the reconnection site.
Key words. Magnetospheric physics
(magnetopause, cusp, and boundary layers; magnetosheath) Space plasma physics
(magnetic reconnection) |
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