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| Titel |
The use of iron charge state changes as a tracer for solar wind entry and energization within the magnetosphere |
| VerfasserIn |
T. A. Fritz, T. H. Zurbuchen, G. Gloeckler, S. Hefti, J. Chen |
| 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 ; 21, no. 11 ; Nr. 21, no. 11, S.2155-2164 |
| Datensatznummer |
250014707
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| Publikation (Nr.) |
 copernicus.org/angeo-21-2155-2003.pdf |
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| Zusammenfassung |
The variation of the
charge state of iron [Fe] ions is used to trace volume elements of plasma in
the solar wind into the magnetosphere and to determine the time scales
associated with the entry into and the action of the magnetospheric
energization process working on these plasmas. On 2–3 May 1998 the Advanced
Composition Explorer (ACE) spacecraft located at the L1 libration point
observed a series of changes to the average charge state of the element Fe in
the solar wind plasma reflecting variation in the coronal temperature of their
original source. Over the period of these two days the average Fe charge state
was observed to vary from + 15 to + 6 both at the Polar satellite in the high
latitude dayside magnetosphere and at ACE. During a period of southward IMF the
observations at Polar inside the magnetosphere of the same Fe charge state were
simultaneous with those at ACE delayed by the measured convection speed of the
solar wind to the subsolar magnetopause. Comparing the phase space density as a
function of energy at both ACE and Polar has indicated that significant
energization of the plasma occurred on very rapid time scales. Energization at
constant phase space density by a factor of 5 to 10 was observed over a range
of energy from a few keV to about 1 MeV. For a detector with a fixed energy
threshold in the range from 10 keV to a few hundred keV this observed
energization will appear as a factor of ~103 increase in its
counting rate. Polar observations of very energetic O+ ions at the same time
indicate that this energization process must be occurring in the high latitude
cusp region inside the magnetosphere and that it is capable of energizing
ionospheric ions at the same time.
Key words. Magnetospheric physics
(magnetopause, cusp, and boundary layers; magnetospheric configuration and
dynamics; solar wind-magnetosphere interactions) |
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