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| Titel |
Conjugate observations of the day-side reconnection electric field: A GEM boundary layer campaign |
| VerfasserIn |
M. Pinnock, A. S. Rodger, K. B. Baker, G. Lu, M. Hairston |
| 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 ; 17, no. 4 ; Nr. 17, no. 4, S.443-454 |
| Datensatznummer |
250013707
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| Publikation (Nr.) |
 copernicus.org/angeo-17-443-1999.pdf |
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| Zusammenfassung |
Data from HF-radars are used to make the
first simultaneous conjugate measurements of the day-side reconnection electric
field. A period of 4 h around local magnetic noon are studied during a geospace
environment modeling (GEM) boundary layer campaign. The interplanetary magnetic
field (IMF) was southward whilst the eastward component (By) was variable. The
flow patterns derived from the radar data show the expected conjugate
asymmetries associated with
IMF |By| > 0. High-time resolution data (50 and 100 s) enable the flow of
plasma across the open/closed field line boundary (the separatrix) to be studied
in greater detail than in previous work. The latitude of the separatrix follows
the same general trend in both hemispheres but shows a hemispherical difference
of 4°, with the summer cusp at higher latitude, as expected from dipole tilt
considerations. However, the short-time scale motion of the separatrix cannot be
satisfactorily resolved within the best resolution (300 m s-1) of the
experiment. The orientation of the separatrix with respect to magnetic latitude
is found to follow the same trend in both hemispheres and qualitatively fits
that predicted by a model auroral oval. It shows no correlation with IMF By.
However, the degree of tilt in the Northern (summer) Hemisphere is found to be
significantly greater than that given by the model oval. The convection pattern
data show that the meridian at which throat flow occurs is different in the two
hemispheres and is controlled by IMF By, in agreement with empirically derived
convection patterns and theoretical models. The day-side reconnection electric
field values are largest when the radar's meridian is in the throat flow or
early afternoon flow regions. In the morning or afternoon convection cells, the
reconnection electric field tends to zero away from the throat flow region. The
reconnection electric field observed in the throat flow region is bursty in
nature.
Key words. Ionosphere (plasma convection; polar
ionosphere) · Magnetospheric physics (magnetosphere-ionosphere interactions) |
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