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| Titel |
Magnetopause energy transfer dependence on the interplanetary magnetic field and the Earth's magnetic dipole axis orientation |
| VerfasserIn |
M. Palmroth, R. C. Fear, I. Honkonen |
| 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 (2012-03-07), S.515-526 |
| Datensatznummer |
250017197
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| Publikation (Nr.) |
 copernicus.org/angeo-30-515-2012.pdf |
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| Zusammenfassung |
| We examine the spatial variation of magnetospheric energy transfer using a
global magnetohydrodynamic (MHD) simulation (GUMICS-4) and a large data set
of flux transfer events (FTEs) observed by the Cluster spacecraft. Our main
purpose is to investigate whether it is possible to validate previous results
on the spatial energy transfer variation from the GUMICS-4 simulation using
the statistical occurrence of FTEs, which are manifestations of
magnetospheric energy transfer. Previous simulation results have suggested
that the energy transfer pattern at the magnetopause rotates according to the
interplanetary magnetic field (IMF) orientation, and here we investigate
whether a similar rotation is seen in the locations at which FTE signatures
are observed. We find that there is qualitative agreement between the
simulation and observed statistics, as the peaks in both distributions rotate
as a function of the IMF clock angle. However, it is necessary to take into
account the modulation of the statistical distribution that is caused by a
bias towards in situ FTE signatures being observed in the winter hemisphere
(an effect that has previously been predicted and observed in this data set).
Taking this seasonal effect into account, the FTE locations support the
previous simulation results and confirm the earlier prediction that the
energy transfers in the plane of the IMF. In addition, we investigate the
effect of the dipole orientation (both the dipole tilt angle and its
orientation in the plane perpendicular to the solar wind flow) on the energy
transfer spatial distribution. We find that the energy transfer occurs mainly
in the summer hemisphere, and that the dayside reconnection region is located
asymmetrically about the subsolar position. Finally, we find that the energy
transfer is 10% larger at equinox conditions than at solstice, contributing
to the discussion concerning the semiannual variation of magnetospheric
dynamics (known as "the Russell-McPherron effect"). |
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