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| Titel |
Long duration Pc 5 compressional pulsations inside the Earth's magnetotail lobes |
| VerfasserIn |
D. V. Sarafopoulos |
| 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 ; 13, no. 9 ; Nr. 13, no. 9, S.926-937 |
| Datensatznummer |
250011977
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| Publikation (Nr.) |
 copernicus.org/angeo-13-926-1995.pdf |
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| Zusammenfassung |
| Pc 5-type magnetic field pulsations are
detected by the IMP-8 spacecraft well inside the Earth's magnetotail lobes. The
three studied events with an average duration of 3 h and mean amplitude of
ΔB/B=6.6% show a strong longitudinal oscillation. The
clockwise polarization sense of the magnetic field arrowheads in the north lobe
(as well as the counterclockwise in the south lobe) on the XZ plane is
consistent with that expected when periodic solar wind lateral pressures squeeze
the magnetotail axisymmetrically while moving tailward. In the two case studies,
the latter property has been found to concur with quasi-periodic upstream
density fluctuations detected by ISEE-3 and/or ISSE-1. The lobe magnetic field
oscillations are classified in two distinct modes. The manifestations of the
first mode are tailward-travelling waves detectable along the By
and Bz magnetic field traces (i.e., with regard to the Bz
the spacecraft encounters constantly the same conspicuous signature of
south-then-north tilting of field lines around each local compression region).
The second mode is associated with prolonged periods of extremely low
geomagnetic activity and exhibits a signature along the By
component inconsistent with travelling waves. Thus, the maxima of compressions
occur simultaneously with the maxima of By excursions: a
feature that is explained in terms of tail-aligned current density flowing at
the boundary which separates the stable magnetic field in the tail lobe from the
very irregular in the magnetosheath. In this case, the spacecraft was located in
the vicinity of the high-latitude tail boundary and the observed By
excursions are consistent with those anticipated by the tail-aligned current
polarity, which is determined by the dominant By-component of
the interplanetary magnetic field (IMF). On the plane YZ we observe an
almost linear and circular polarization sense of the vector magnetic field for
the first and second mode, respectively. |
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