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| Titel |
Centrifugal acceleration in the magnetotail lobes |
| VerfasserIn |
H. Nilsson, E. Engwall, A. Eriksson, P. A. Puhl-Quinn, S. Arvelius |
| 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 ; 28, no. 2 ; Nr. 28, no. 2 (2010-02-15), S.569-576 |
| Datensatznummer |
250016784
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| Publikation (Nr.) |
 copernicus.org/angeo-28-569-2010.pdf |
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| Zusammenfassung |
| Combined Cluster EFW and EDI measurements have shown that cold ion outflow in
the magnetospheric lobes dominates the hydrogen ion outflow from the Earth's
atmosphere. The ions have too low kinetic energy to be measurable with
particle instruments, at least for the typical spacecraft potential of a
sunlit spacecraft in the tenuous lobe plasmas outside a few RE. The
measurement technique yields both density and bulk velocity, which can be
combined with magnetic field measurements to estimate the centrifugal
acceleration experienced by these particles. We present a quantitative
estimate of the centrifugal acceleration, and the velocity change with
distance which we would expect due to centrifugal acceleration. It is found
that the centrifugal acceleration is on average outward with an average value
of about of 5 m s−2. This is small, but acting during long
transport times and over long distances the cumulative effect is significant,
while still consistent with the relatively low velocities estimated using the
combination of EFW and EDI data. The centrifugal acceleration should
accelerate any oxygen ions in the lobes to energies observable by particle
spectrometers. The data set also put constraints on the effectiveness of any
other acceleration mechanisms acting in the lobes, where the total velocity
increase between 5 and 19 RE geocentric distance is less than 5 km s−1. |
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