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| Titel |
Plasma flows, Birkeland currents and auroral forms in relation to the Svalgaard-Mansurov effect |
| VerfasserIn |
P. E. Sandholt, C. J. Farrugia |
| 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. 5 ; Nr. 30, no. 5 (2012-05-09), S.817-830 |
| Datensatznummer |
250017223
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| Publikation (Nr.) |
 copernicus.org/angeo-30-817-2012.pdf |
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| Zusammenfassung |
| The traditional explanation of the
polar cap magnetic deflections, referred to as the
Svalgaard-Mansurov effect, is in
terms of currents associated with
ionospheric flow resulting from
the release of magnetic tension on newly open magnetic field lines.
In this study, we aim at an updated description of the sources of
the Svalgaard-Mansurov effect based on recent
observations of configurations of plasma flow
channels, Birkeland current systems and aurorae
in the magnetosphere-ionosphere system.
Central to our description is the distinction between
two different flow channels (FC 1 and FC 2) corresponding to
two consecutive stages in the evolution of
open field lines in Dungey cell convection,
with FC 1 on newly open, and FC 2 on
old open, field lines. Flow channel FC 1 is the result of
ionospheric Pedersen current closure of
Birkeland currents flowing along newly open field lines.
During intervals of nonzero interplanetary magnetic field By
component FC 1 is observed on either side of noon
and it is accompanied by
poleward moving auroral forms
(PMAFs/prenoon and PMAFs/postnoon). In such cases
the next convection stage, in the form of flow channel FC 2 on the periphery
of the polar cap, is particularly important for
establishing an IMF By-related convection
asymmetry along the dawn-dusk meridian, which is a central
element causing the Svalgaard-Mansurov effect.
FC 2 flows are excited by the ionospheric Pedersen
current closure of the northernmost pair of Birkeland currents
in the four-sheet current system, which is coupled to the
tail magnetopause and flank low-latitude boundary layer.
This study is based on a review of
recent statistical and event studies of central parameters
relating to the magnetosphere-ionosphere current systems mentioned above.
Temporal-spatial structure in the current systems
is obtained by ground-satellite
conjunction studies. On this point
we emphasize the important information derived from
the continuous ground monitoring of
the dynamical behaviour of aurora and plasma convection
during intervals of well-organised solar wind plasma and
magnetic field conditions in interplanetary coronal mass ejections
(ICMEs) during their Earth passage. |
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