 |
| Titel |
Comparison of eight years magnetic field data from Cluster with Tsyganenko models in the inner magnetosphere |
| VerfasserIn |
Q.-H. Zhang, M. W. Dunlop, R. Holme, E. E. Woodfield |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 28, no. 1 ; Nr. 28, no. 1 (2010-01-29), S.309-326 |
| Datensatznummer |
250016763
|
| Publikation (Nr.) |
 copernicus.org/angeo-28-309-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
| Eight years of magnetic field data, taken while the four Cluster spacecraft
pass through, or adjacent to, the equatorial ring current, have been
surveyed to investigate the effects on the Earth's magnetic field of the
externally driven current systems connecting the ionosphere, cusp and ring
current regions. This study extends previous work to cover a greater range
of orbit location and external conditions. We compare the modeled magnetic
field from different global field models (Tsyganenko, 1989, 1996, and 2001,
hereafter T89, T96 and T01) with data from the four Cluster spacecraft.
Comparing with the different models allow us not only to characterize each
model's performance, but also provides insight into the physical sources of
observed signals. The data generally deviate much less from the expected
model field during the years close to the solar minimum, implying that the
models perform better during weaker geomagnetic activity. There are
particular deviations from the models associated with the ring current
(well-defined smooth trends) and region 2 field aligned currents (FACs) or
low-altitude cusp FACs (sharp bipolar signatures). During the ring current
crossings (through perigee, at 4–5 RE), the T96 model always overestimates
the ring current, while the T01 and T89 models sometimes underestimate it.
The sharp bipolar signatures are not always sampled, implying a localized
extent, but only the T96 and T01 models include forms for the region 2 FACs
and T01 appears to model these better. Overall, all deviations from T01 are
much smaller than for the other models, indicating that this model achieves
the best fit to the data. The 4 Cluster spacecraft observe nearly the same
signatures at small separations (during the early years of the mission) but
do sample different signatures at the large separations (during the later
years). Using the four-spacecraft technique, we infer that the region 2
FACs, with a transverse thickness of ~0.17–0.54 RE, and cusp
FACs, with a thickness of ~0.06–0.12 RE, are very stable in size
and location. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|