期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
卷 119, 期 1, 页码 375-383出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2013JA019352
关键词
equatorial ionosphere; spread F; satellite trace; LSWS; Rayleigh-Taylor Instability; ESF initiation
资金
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) [CNPq 300883/2008-0]
- AF grant [FA8718-06-C-0072]
A better understanding of the precursor conditions for the instability growth is very important for identifying the causes of day-to-day variability in the equatorial spread F (ESF)/plasma bubble irregularity development. We investigate here the satellite trace (S-trace) in the ionograms, a precursor to the postsunset ESF occurrence, as observed by Digisondes operated at an equatorial and two magnetic conjugate sites in Brazil during a 66day observational campaign (Conjugate Point Equatorial Experiment 2002). The satellite traces first occur at the equatorial site, and sequentially, after a variable delay of approximately 20 to 50min, they are observed nearly simultaneously over the two conjugate sites. The evening prereversal enhancement in the zonal electric field/vertical drift is found to control its development. Using a three-dimensional simulation code based on collisional interchange instability mechanism, it is shown that the observed S-trace occurrence sequence is fully consistent with the instability initiation over the equator with the field-aligned plasma depletion vertical growth marked by latitudinal expansion of its extremities to conjugate locations. The delay in the S-trace occurrence at the conjugate sites (a measure of the nonlinear growth of the instability for plasma depletion) is controlled also by field line parallel (meridional) neutral wind. The relationship between the S-trace and the large-scale wave structure in the F layer, another widely known characterization of the precursor condition for the ESF development, is also clarified.
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