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| Titel |
Seasonal and magnetic activity variations of ionospheric electric fields above the southern mid-latitude station, Bundoora, Australia |
| VerfasserIn |
M. L. Parkinson, R. Polglase, B. G. Fejer, L. Scherliess, P. L. Dyson, S. M. Ujmaia |
| 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 ; 19, no. 5 ; Nr. 19, no. 5, S.521-532 |
| Datensatznummer |
250014251
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| Publikation (Nr.) |
 copernicus.org/angeo-19-521-2001.pdf |
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| Zusammenfassung |
We investigate the
seasonal, local solar time, and geomagnetic activity variations of the average
Doppler velocity measured by an HF digital ionosonde deployed at Bundoora,
Australia (145.1° E, 37.7° S, geographic; 49° S magnetic). The Doppler
velocities were heavily averaged to suppress the short-term effects (<3
hours) of atmospheric gravity waves, and thereby obtain the diurnal variations
attributed to the tidally-driven ionospheric dynamo and electric fields
generated by magnetic disturbances. The observed seasonal variations in Doppler
velocity were probably controlled by variations in the lower thermospheric winds
and ionospheric conductivity above Bundoora and in the magnetically conjugate
location. The diurnal variations of the meridional (field-perpendicular) drifts
and their perturbations exhibited a complex structure, and were generally
smaller than the variations in the zonal drifts. The latter were basically
strongly west-ward during the evening to early morning, and weakly east-ward
during the late morning to just past noon. The zonal perturbations were strongly
enhanced by increasing geomagnetic activity, and closely resembled the
perturbation drifts measured by the incoherent scatter radar (ISR) at Millstone
Hill (71.5° W, 42.6° N; 57° N). There was also some resemblance between the
diurnal variations in the meridional drifts. Overall, the comparisons suggest
that with sufficient averaging, Doppler velocities measured with digital
ionosondes at mid-latitudes correspond to true ion motions driven by ionospheric
electric fields. This is a useful result because apart from the ISRs located in
the American-European sector, there are no ground-based instruments capable of
measuring electric fields in the mid-latitude ionosphere.
Key words. Ionosphere (electric
fields and currents; ionosphere atmosphere interactions; mid-latitude
ionosphere) |
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