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| Titel |
New plasmapause model derived from CHAMP field-aligned current signatures |
| VerfasserIn |
B. Heilig, H. Lühr |
| 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 ; 31, no. 3 ; Nr. 31, no. 3 (2013-03-19), S.529-539 |
| Datensatznummer |
250019012
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| Publikation (Nr.) |
 copernicus.org/angeo-31-529-2013.pdf |
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| Zusammenfassung |
| We introduce a new model for the plasmapause location in the equatorial
plane. The determination of the L-shell bounding the plasmasphere is based on
magnetic field observations made by the CHAMP satellite in the topside
ionosphere. Related signals are medium-scale field-aligned currents (MSFAC)
(some 10 km scale size). The mid-latitude boundary of these MSFACs is used for
determining the plasmapause. We are presenting a procedure for detecting the
MSFAC boundary. Reliable L-values are obtained on the night side, whenever
the solar zenith angle is below 90°. This means, the boundary is not
determined well in the 08:00 to 16:00 magnetic local time (MLT) sector. The
radial distance of the boundary is closely controlled by the magnetic
activity index Kp. Over the Kp range 0 to 9, the L-value varies from 6 to
2 RE. Conversely, the dependence on solar flux is insignificant. For a
fixed Kp level, the obtained L-values of the boundary form a ring on an MLT
dial plot with a centre somewhat offset from the geomagnetic pole. This Kp
and local time dependent feature is used for predicting the location of the
MSFAC boundary at all MLTs based on a single L-value determination by CHAMP.
We compared the location of the MSFAC boundary during the years 2001–2002
with the L-value of the plasmapause, determined from in situ observations by
the IMAGE spacecraft. The mean difference in radial distance is within a
1 RE range for all local times and Kp values. The plasmapause is generally
found earthward of the FAC boundary, except for the duskside. By considering
this systematic displacement and by taking into account the diurnal variation
and Kp-dependence of the residuals, we are able to construct an empirical
model of the plasmapause location that is based on MSFAC measurements from
CHAMP. Our new model PPCH-2012 agrees with IMAGE in situ observations within
a standard deviation of 0.79 RE. |
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