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| Titel |
The dayside magnetopause location during radial interplanetary magnetic field periods: Cluster observation and model comparison |
| VerfasserIn |
T. Huang, H. Wang, J.-H. Shue, L. Cai, G. Pi |
| 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 ; 33, no. 4 ; Nr. 33, no. 4 (2015-04-02), S.437-448 |
| Datensatznummer |
250121186
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| Publikation (Nr.) |
 copernicus.org/angeo-33-437-2015.pdf |
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| Zusammenfassung |
| The present work has investigated the midlatitudinal magnetopause
locations under radial interplanetary field (RIMF) conditions.
Among 262 (256) earthward (sunward) RIMF events from years of 2001
to 2009, Cluster satellites have crossed the magnetopause 22(12)
times, with 10 (7) events occurring at midlatitudes. The observed
midlatitudinal magnetopause positions are compared with two
empirical magnetopause models (Shue et al., 1998; Boardsen et al.,
2000) (hereafter referred to as the Shue98 model and the Boardsen00 model). The
observation–model differences exhibit local time asymmetry. For
earthward RIMF cases, the Shue98 model underestimates the magnetopause
positions in the postnoon sector, while it overestimates the
magnetopause positions in the dawn and dusk sectors. The Boardsen00
model generally underestimates the magnetopause after 6 MLT (magnetic local time), with
larger deviations in the postnoon sector as compared to those in
the prenoon. For sunward RIMF cases, the selected events are
mainly clustered around the dawn and dusk sectors. The comparison with
the Shue98 model indicates contractions in the dawn and expansions in
the dusk sector, while the comparison with Boardsen00 indicates general expansions, with larger expansions in the later local
time sectors. The local time variations in the differences between
observations and the Shue98 and the Boardsen00 models indicate that the real
magnetopause could be asymmetrically shaped during radial IMF
periods, which should be considered by magnetopause models. The
observation–model differences in the magnetopause positions
(Δ RMP) during RIMF periods correlate well with the
solar wind dynamic pressure, with larger Δ RMP
for larger Pd. The southern magnetopause expands further outward
relative to the model prediction when the dipole tilt angle is more
negative (local summer in the Southern Hemisphere). For earthward
RIMF cases, the generally good correlations between Δ RMP
and the IMF cone angle are consistent with the previous hypothesis
(Dušík et al., 2010) that, with more radial IMF, the subsolar magnetopause
will expand further outward, owever, this is not the case for the comparison with Boardsen00 during sunward IMF periods, as it shows less dependence on the IMF cone angle. |
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