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| Titel |
Magnetospheric solitary structure maintained by 3000 km/s ions as a cause of westward moving auroral bulge at 19 MLT |
| VerfasserIn |
M. Yamauchi, I. Dandouras, P. W. Daly, G. Stenberg, H. U. Frey, P.-A. Lindqvist, Y. Ebihara, H. Nilsson, R. Lundin, H. Rème, M. André, E. A. Kronberg, A. Balogh, M. Henderson |
| 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 ; 27, no. 7 ; Nr. 27, no. 7 (2009-07-27), S.2947-2969 |
| Datensatznummer |
250016603
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| Publikation (Nr.) |
 copernicus.org/angeo-27-2947-2009.pdf |
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| Zusammenfassung |
| In the evening equatorial magnetosphere at about 4 RE geocentric
distance and 19 MLT, the four Cluster spacecraft observed a solitary
structure with a width of about 1000~2000 km in the propagation
direction. The solitary structure propagates sunward with about 5~10 km/s
carrying sunward electric field (in the propagation direction) of up to
about 10 mV/m (total potential drop of about 5~10 kV), depletion of
magnetic field of about 25%, and a duskward E×B convection up to 50 km/s
of He+ rich cold plasma without O+. At the same time, auroral
images from the IMAGE satellite together with ground based geomagnetic field
data showed a westward (sunward at this location) propagating auroral bulge
at the magnetically conjugate ionosphere with the solitary structure. The
solitary structure is maintained by flux enhancement of selectively 3000 km/s
ions (about 50 keV for H+, 200 keV for He+, and 750 keV for O+).
These ions are the main carrier of the diamagnetic current causing the
magnetic depletion, whereas the polarization is maintained by different
behavior of energetic ions and electrons. Corresponding to aurora,
field-aligned accelerated ionospheric plasma of several keV appeared at
Cluster from both hemispheres simultaneously. Together with good
correspondence in location and propagation velocity between the auroral bulge
and the solitary structure, this indicates that the sunward moving auroral
bulge is caused by the sunward propagation of the solitary structure which is
maintained by energetic ions. The solitary structure might also be the cause
of Pi2-like magnetic variation that started simultaneously at Cluster
location. |
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