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| Titel |
Study of the applicability of the curlometer technique with the four Cluster spacecraft in regions close to Earth |
| VerfasserIn |
S. Grimald, I. Dandouras, P. Robert, E. Lucek |
| 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 ; 30, no. 3 ; Nr. 30, no. 3 (2012-03-27), S.597-611 |
| Datensatznummer |
250017205
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| Publikation (Nr.) |
 copernicus.org/angeo-30-597-2012.pdf |
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| Zusammenfassung |
| Knowledge of the inner magnetospheric current system (intensity, boundaries,
evolution) is one of the key elements for the understanding of the whole
magnetospheric current system. In particular, the calculation of the current
density and the study of the changes in the ring current is an active field
of research as it is a good proxy for the magnetic activity. The curlometer
technique allows the current density to be calculated from the magnetic
field measured at four different positions inside a given current sheet
using the Maxwell-Ampere's law. In 2009, the CLUSTER perigee pass was located
at about 2 RE allowing a study of the ring current deep inside the
inner magnetosphere, where the pressure gradient is expected to invert
direction. In this paper, we use the curlometer in such an orbit. As the
method has never been used so deep inside the inner magnetosphere, this
study is a test of the curlometer in a part of the magnetosphere where the
magnetic field is very high (about 4000 nT) and changes over small distances
(ΔB = 1nT in 1000 km). To do so, the curlometer has been applied to
calculate the current density from measured and modelled magnetic fields and
for different sizes of the tetrahedron. The results show that the current
density cannot be calculated using the curlometer technique at low altitude
perigee passes, but that the method may be accurate in a [3 RE; 5 RE]
or a [6 RE; 8.3 RE] L-shell range. It also demonstrates
that the parameters used to estimate the accuracy of the method are
necessary, but not sufficient conditions. |
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