Advanced search
Start date
(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Gravity wave initiation of equatorial spread F/plasma bubble irregularities based on observational data from the SpreadFEx campaign

Full text
Abdu, M. A. [1] ; Kherani, E. Alam [1] ; Batista, I. S. [1] ; de Paula, E. R. [1] ; Fritts, D. C. [2] ; Sobral, J. H. A. [1]
Total Authors: 6
[1] Inst Nacl Pesquisas Espaciais, BR-12201 Sao Jose Dos Campos - Brazil
[2] NW Res Associates Inc, Colorado Res Associates Div, Boulder, CO - USA
Total Affiliations: 2
Document type: Journal article
Source: Annales Geophysicae; v. 27, n. 7, p. 2607-2622, 2009.
Web of Science Citations: 106

The data from ground based experiments conducted during the 2005 SpreadFEx campaign in Brazil are used, with the help of theoretical model calculations, to investigate the precursor conditions, and especially, the role of gravity waves, in the instability initiation leading to equatorial spread F development. Data from a digisonde and a 30MHz coherent back-scatter radar operated at an equatorial site, Sao Luis (dip angle: 2.7 degrees) and from a digisonde operated at another equatorial site (dip angle: -11.5 degrees) are analyzed during selected days representative of differing precursor conditions of the evening prereversal vertical drift, F layer bottom-side density gradients and density perturbations due to gravity waves. It is found that radar irregularity plumes indicative of topside bubbles, can be generated for precursor vertical drift velocities exceeding 30 m/s even when the precursor GW induced density oscillations are marginally detectable by the digisonde. For drift velocities <= 20 m/s the presence of precursor gravity waves of detectable intensity is found to be a necessary condition for spread F instability initiation. Theoretical model calculations show that the zonal polarization electric field in an instability development, even as judged from its linear growth phase, can be significantly enhanced under the action of perturbation winds from gravity waves. Comparison of the observational results with the theoretical model calculations provides evidence for gravity wave seeding of equatorial spread F. (AU)

FAPESP's process: 99/00437-0 - Studies of the interactive processes of the equatorial ionosphere-thermosphere system
Grantee:Mangalathayil Ali Abdu
Support Opportunities: Research Projects - Thematic Grants