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| Titel |
Equinoctial asymmetry of a low-latitude ionosphere-thermosphere system and equatorial irregularities: evidence for meridional wind control |
| VerfasserIn |
T. Maruyama, S. Saito, M. Kawamura, K. Nozaki, J. Krall, J. D. Huba |
| 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 ; 27, no. 5 ; Nr. 27, no. 5 (2009-05-04), S.2027-2034 |
| Datensatznummer |
250016521
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| Publikation (Nr.) |
 copernicus.org/angeo-27-2027-2009.pdf |
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| Zusammenfassung |
| Nocturnal ionospheric height variations were analyzed along the meridian of
100° E by using ionosonde data. Two ionosondes were installed near the
magnetic conjugate points at low latitudes, and the third station was
situated near the magnetic equator. Ionospheric virtual heights were scaled
every 15 min and vertical E×B drift velocities
were inferred from the equatorial station. By incorporating the inferred
equatorial vertical drift velocity, ionospheric bottom heights with the
absence of wind were modeled for the two low-latitude conjugate stations,
and the deviation in heights from the model outputs was used to infer the
transequatorial meridional thermospheric winds. The results obtained for the
September and March equinoxes of years 2004 and 2005, respectively, were
compared, and a significant difference in the meridional wind was found. An
oscillation with a period of approximately 7 h of the meridional wind
existed in both the equinoxes, but its amplitude was larger in September as
compared to that in March. When the equatorial height reached the maximum
level due to the evening enhancement of the zonal electric field, the
transequatorial meridional wind velocity reached approximately 10 and 40 m/s
for the March and September equinoxes, respectively. This asymmetry of the
ionosphere-thermosphere system was found to be associated with the
previously reported equinoctial asymmetry of equatorial ionospheric
irregularities; the probability for equatorial irregularities to occur is
higher in March as compared to that in September at the Indian to Western
Pacific longitudes. Numerical simulations of plasma bubble developments were
conducted by incorporating the transequatorial neutral wind effect, and the
results showed that the growth time (e-folding time) of the bubble was
halved when the wind velocity changed from 10 to 40 m/s. |
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