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| Titel |
A statistical study of intense electric fields at 4-7 RE geocentric distance using Cluster |
| VerfasserIn |
T. Johansson, T. Karlsson, G. Marklund, S. Figueiredo, P.-A. Lindqvist, S. Buchert |
| 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 ; 23, no. 7 ; Nr. 23, no. 7 (2005-10-14), S.2579-2588 |
| Datensatznummer |
250015331
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| Publikation (Nr.) |
 copernicus.org/angeo-23-2579-2005.pdf |
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| Zusammenfassung |
Intense high-latitude electric fields (>150 mV/m mapped to
ionospheric altitude) at 4–7 RE geocentric distance have been
investigated in a statistical study, using data from the Cluster
satellites. The orbit of the Cluster satellites limits the data
collection at these altitudes to high latitudes, including the
poleward part of the auroral oval. The occurrence and distribution
of the selected events have been used to characterize the intense
electric fields and to investigate their dependance on parameters
such as MLT, CGLat, altitude, and also Kp. Peaks in the local time
distribution are found in the evening to morning sectors but also
in the noon sector, corresponding to cusp events. The electric
field intensities decrease with increasing latitude in the region
investigated (above 60 CGLat). A dependence on geomagnetic
activity is indicated since the probability of finding an event
increases up to Kp=5–6. The scales sizes are in the range up to
10 km (mapped to ionospheric altitude) with a maximum around 4–5km,
consistent with earlier findings at lower altitudes and Cluster
event studies. The magnitudes of the electric fields are inversely
proportional to the scale sizes. The type of electric field
structure (convergent or divergent) is consistent with the FAC
direction for a subset of events with electric field intensities
in the range 500–1000 mV/m and with clear bipolar signatures. The FAC
directions are also consistent with the Region 1 and NBZ current
systems, the latter of which prevail only during northward IMF
conditions. For scale sizes less than 2 km the majority of the
events were divergent electric field structures. Both converging
and diverging electric fields were found throughout the
investigated altitude range (4–7 RE
geocentric distance).
Keywords. Magnetospheric physics (Electric fields; Auroral
phenomena; Magnetosphere-ionosphere interactions) |
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