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| Titel |
Cluster observations of near-Earth magnetospheric lobe plasma densities – a statistical study |
| VerfasserIn |
K. R. Svenes, B. Lybekk, A. Pedersen, S. Haaland |
| 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 ; 26, no. 9 ; Nr. 26, no. 9 (2008-09-22), S.2845-2852 |
| Datensatznummer |
250016232
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| Publikation (Nr.) |
 copernicus.org/angeo-26-2845-2008.pdf |
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| Zusammenfassung |
| The Cluster-mission has enabled a study of the near-Earth magnetospheric
lobes throughout the waning part of solar cycle 23. During the first seven
years of the mission the satellites crossed this region of space regularly
from about July to October. We have obtained new and more accurate
plasma densities in this region based on spacecraft potential measurements
from the EFW-instrument. The plasma density measurements are found by
converting the potential measurements using a functional relationship
between these two parameters. Our observations have shown that throughout
this period a full two thirds of the measurements were contained in the
range 0.007–0.092 cm−3 irrespective of solar wind conditions or
geomagnetic activity. In fact, the most probable density encountered was
0.047 cm−3, staying roughly constant throughout the entire observation
period. The plasma population in this region seems to reflect an equilibrium
situation in which the density is independent of the solar wind condition or
geomagnetic activity. However, the high density tail of the population
(ne>0.2 cm−3) seemed to decrease with the waning solar cycle.
This points to a source region influenced by the diminishing solar
UV/EUV-intensity. Noting that the quiet time polar wind has just such a
development and that it is magnetically coupled to the lobes, it seems
likely to assume that this is a prominent source for the lobe plasma. |
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