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| Titel |
Observations of the generation of eastward equatorial electric fields near dawn |
| VerfasserIn |
M. C. Kelley, F. S. Rodrigues, R. F. Pfaff, J. Klenzing |
| 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 ; 32, no. 9 ; Nr. 32, no. 9 (2014-09-19), S.1169-1175 |
| Datensatznummer |
250121111
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| Publikation (Nr.) |
 copernicus.org/angeo-32-1169-2014.pdf |
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| Zusammenfassung |
| We report and discuss interesting observations of the variability of electric
fields and ionospheric densities near sunrise in the equatorial ionosphere
made by instruments onboard the Communications/Navigation Outage Forecasting
System (C/NOFS) satellite over six consecutive orbits. Electric field
measurements were made by the Vector Electric Field Instrument (VEFI), and
ionospheric plasma densities were measured by Planar Langmuir Probe (PLP).
The data were obtained on 17 June 2008, a period of solar minimum conditions.
Deep depletions in the equatorial plasma density were observed just before
sunrise on three orbits, for which one of these depletions was accompanied by
a very large eastward electric field associated with the density depletion,
as previously described by de La Beaujardière et al. (2009), Su et
al. (2009) and Burke et al. (2009). The origin of this large eastward field
(positive upward/meridional drift), which occurred when that component of the
field is usually small and westward, is thought to be due to a large-scale
Rayleigh–Taylor process. On three subsequent orbits, however, a distinctly
different, second type of relationship between the electric field and plasma
density near dawn was observed. Enhancements of the eastward electric field
were also detected, one of them peaking around 3 mV m−1, but they were
found to the east (later local time) of pre-dawn density perturbations. These
observations represent sunrise enhancements of vertical drifts accompanied by
eastward drifts such as those observed by the San Marco satellite (Aggson et
al., 1995). Like the San Marco measurements, the enhancements occurred during
winter solstice and low solar flux conditions in the Pacific longitude
sector. While the evening equatorial ionosphere is believed to present the
most dramatic examples of variability, our observations exemplify that the
dawn sector can be highly variable as well. |
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