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| Titel |
First simultaneous measurements of waves generated at the bow shock in the solar wind, the magnetosphere and on the ground |
| VerfasserIn |
L. B. N. Clausen, T. K. Yeoman, R. C. Fear, R. Behlke, E. A. Lucek, M. J. Engebretson |
| 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. 1 ; Nr. 27, no. 1 (2009-01-22), S.357-371 |
| Datensatznummer |
250016377
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| Publikation (Nr.) |
 copernicus.org/angeo-27-357-2009.pdf |
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| Zusammenfassung |
| On 5 September 2002 the Geotail satellite observed the cone angle of the
Interplanetary Magnetic Field (IMF) change to values below 30° during
a 56 min interval between 18:14 and 19:10 UT. This triggered the generation
of upstream waves at the bow shock, 13 RE downstream of the position
of Geotail. Upstream generated waves were subsequently observed by Geotail
between 18:30 and 18:48 UT, during times the IMF cone angle dropped below
values of 10°. At 18:24 UT all four Cluster satellites simultaneously
observed a sudden increase in wave power in all three magnetic field
components, independent of their position in the dayside magnetosphere. We
show that the 10 min delay between the change in IMF direction as observed
by Geotail and the increase in wave power observed by Cluster is consistent
with the propagation of the IMF change from the Geotail position to the bow
shock and the propagation of the generated waves through the bow shock,
magnetosheath and magnetosphere towards the position of the Cluster
satellites. We go on to show that the wave power recorded by the Cluster
satellites in the component containing the poloidal and compressional
pulsations was broadband and unstructured; the power in the component
containing toroidal oscillations was structured and shows the existence of
multi-harmonic Alfvénic continuum waves on field lines. Model predictions
of these frequencies fit well with the observations. An increase in wave
power associated with the change in IMF direction was also registered by
ground based magnetometers which were magnetically conjunct with the Cluster
satellites during the event. To the best of our knowledge we present the
first simultaneous observations of waves created by backstreaming ions at the
bow shock in the solar wind, the dayside magnetosphere and on the ground. |
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