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| Titel |
Influence of the finite ionospheric conductivity on dispersive, nonradiative field line resonances |
| VerfasserIn |
A. Streltsov, W. Lotko |
| 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 ; 15, no. 6 ; Nr. 15, no. 6, S.625-633 |
| Datensatznummer |
250012822
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| Publikation (Nr.) |
 copernicus.org/angeo-15-625-1997.pdf |
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| Zusammenfassung |
| The influence of the finite ionospheric
conductivity on the structure of dispersive, nonradiative field line resonances
(FLRs) is investigated for the first four odd harmonics. The results are based
on a linear, magnetically incompressible, reduced, two-fluid MHD model. The
model includes effects of finite electron inertia (at low altitude) and finite
electron pressure (at high altitude). The ionosphere is treated as a
high-integrated conducting substrate. The results show that even very low
ionospheric conductivity (ΣP = 2 mho) is not
sufficient to prevent the formation of a large-amplitude, small-scale,
nonradiative FLR for the third and higher harmonics when the background
transverse plasma inhomogeneity is strong enough. At the same time, the
fundamental FLR is strongly affected by a state of low conductivity, and when
ΣP = 2 mho, this resonance forms only
small-amplitude, relatively broad electromagnetic disturbance. The difference in
conductivities of northern and southern ionospheres does not produce significant
asymmetry in the distribution of electric and magnetic fields along the resonant
field line. The transverse gradient of the background Alfvén speed plays an
important role in structure of the FLR when the ionospheric conductivity is
finite. In cases where the transverse inhomogeneity of the plasma is not strong
enough, the low ionospheric conductivity can prevent even higher-harmonic FLRs
from contracting to small scales where dispersive effects are important. The
application of these results to the formation and temporal evolution of
small-scale, active auroral arc forms is discussed. |
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