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| Titel |
Comparison of the observed dependence of large-scale Birkeland currents on solar wind parameters with that obtained from global simulations |
| VerfasserIn |
H. Korth, L. Rastätter, B. J. Anderson, A. J. Ridley |
| 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 ; 29, no. 10 ; Nr. 29, no. 10 (2011-10-18), S.1809-1826 |
| Datensatznummer |
250017108
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| Publikation (Nr.) |
 copernicus.org/angeo-29-1809-2011.pdf |
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| Zusammenfassung |
| Spatial distributions of the large-scale Birkeland currents derived from
magnetic field data acquired by the constellation of Iridium Communications
satellites have been compared with global-magnetosphere magneto-hydrodynamic
(MHD) simulations. The Iridium data, spanning the interval from February 1999
to December 2007, were first sorted into 45°-wide bins of the
interplanetary magnetic field (IMF) clock angle, and the dependencies of the
Birkeland currents on solar wind electric field magnitude, Eyz,
ram pressure, psw, and Alfvén Mach number, MA,
were then examined within each bin. The simulations have been conducted at
the publicly-accessible Community Coordinated Modeling Center using the
University of Michigan Space Weather modeling Framework, which features a
global magnetosphere model coupled to the Rice Convection Model. In excess of
120 simulations with steady-state conditions were executed to yield the
dependencies of the Birkeland currents on the solar wind and IMF parameters
of the coupled model. Averaged over all IMF orientations, the simulation
reproduces the Iridium statistical Birkeland current distributions with a
two-dimensional correlation coefficient of about 0.8, and the total current
agrees with the climatology averages to within 10%. The total current for
individual events regularly exceeds those computed from statistical
distributions by factors of ≥2, resulting in larger disparities between
observations and simulations. The simulation results also qualitatively
reflect the observed increases in total current with increasing
Eyz and psw, but the model underestimates the rate of
increase by up to 50%. The equatorward expansion and shift of the
large-scale currents toward noon observed for increasing Eyz are
also evident in the simulation current patterns. Consistent with the
observations, the simulation does not show a significant dependence of the
total current on MA. |
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