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| Titel |
Simultaneous ionospheric and magnetospheric observations of azimuthally propagating transient features during substorms |
| VerfasserIn |
T. K. Yeoman, T. Mukai, T. Yamamoto |
| 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 ; 16, no. 7 ; Nr. 16, no. 7, S.754-763 |
| Datensatznummer |
250013336
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| Publikation (Nr.) |
 copernicus.org/angeo-16-754-1998.pdf |
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| Zusammenfassung |
During the 6th August 1995, the
CUTLASS Finland HF radar ran in a high time resolution mode, allowing
measurements of line-of-sight convection velocities along a single beam with a
temporal resolution of 14 s. Data from such scans, during the substorm expansion
phase, revealed pulses of equatorward flow exceeding ~600 m s–1 with
a duration of ~5 min and a repetition period of ~8 min. Each pulse of enhanced
equatorward flow was preceded by an interval of suppressed flow and enhanced
ionospheric Hall conductance. These transient features, which propagate
eastwards away from local midnight, have been interpreted as ionospheric current
vortices associated with field-aligned current pairs. The present study reveals
that these ionospheric convection features appear to have an accompanying
signature in the magnetosphere, comprising a dawnward perturbation and
dipolarisation of the magnetic field and dawnward plasma flow, measured in the
geomagnetic tail by the Geotail spacecraft, located at L = 10 and
some four hours to the east, in the postmidnight sector. These signatures are
suggested to be the consequence of the observation of the same field aligned
currents in the magnetosphere. Their possible relationship with bursty Earthward
plasma flow and magnetotail reconnection is discussed.
Key words. Ionosphere (Auroral · ionosphere) ·
Magnetospheric Physics (Magnetotail; Storms and substorms) |
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