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| Titel |
Characteristics of the terrestrial field-aligned current system |
| VerfasserIn |
J. W. Gjerloev, S. Ohtani, T. Iijima, B. Anderson, J. Slavin, G. Le |
| 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 (2011-10-04), S.1713-1729 |
| Datensatznummer |
250017100
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| Publikation (Nr.) |
 copernicus.org/angeo-29-1713-2011.pdf |
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| Zusammenfassung |
| We present the first ever comprehensive statistical study of the
spatiotemporal characteristics of field-aligned currents in the terrestrial
magnetosphere-ionosphere system using multi point measurements. We determine
how the FAC density, variability and scale size are coupled. The three ST 5
satellites were in a pearls-on-a-string formation making measurements of the
magnetic field with variable inter-spacecraft separations ranging from a few
seconds to about 10 min. More than 4700 sets of satellite passes are
analyzed using a robust correlation analysis aimed at determining the
variability of the FAC system as a function of scale size and satellite
spacing. We find significant differences between the FAC characteristics on
the dayside and on the nightside in terms of dynamics of the current
systems. On the dayside the FAC characteristics are found to be independent
of IMF Bz and geomagnetic activity while the nightside indicates increased
variability during disturbed conditions. The boundary separating highly and
poorly correlated FACs can be fitted by a linear line for satellite
separations shorter than 60 s (dayside) and 160 s (nightside). We interpret
this as the dayside and nightside magnetospheric reconfiguration times
respectively. For times exceeding this the FAC characteristics are suggested
to be controlled by the solar wind (dayside) and plasma sheet (nightside)
dynamics. Finally, the characteristics of FAC system with scale sizes larger
than ~200 km (at ionospheric altitude) appear to be stable and
repeatable on time scales of the order of a minute (i.e. comparable to the
low-altitude orbiting satellite's traverse time across the auroral belt). In
this sense, our results effectively validate the Iijima and Potemra (1978) assumption that on
average the large-scale currents with scale sizes of the Region1 and Region2
are quasi-persistently significant in the transport of energy and momentum
between the magnetosphere and the ionosphere. |
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