ALTAIR Radar Study of Equatorial Spread F.
Abstract
The results of research on equatorial spread-F (ESF) phenomena obtained by using two backscatter radars, ALTAIR and TRADEX, are summarized. The radar measurements were made in support of three rocket campaigns conducted from the Kwajalein Atoll during the summers of 1977 through 1979. Backscatter data from ESF irregularities and incoherent-scatter (IS) data from thermal plasma fluctuations were used to show that the structuring of the equatorial F-region plasma is initiated by large-scale (tens to a few hundred kilometers in the east-west direction) plasma-density modulations in the bottomside F layer. The modulation, best described by wavelike altitude variations in constant electron-density contours, appears to be imposed on the bottomside F layer around E-region sunset by a yet-to--be-identified source (although atmospheric gravity waves are a likely candidate). The amplification of the wavelike modulation, in the form of upwellings from the crests of the modulation, is consistent with the amplification expected from the collisional Rayleigh-Taylor instability. Once the upwellings begin to grow in altitude extent, the west walls become unstable via the gradient-drift instability, driven by an eastward neutral wind blowing through the walls of the upwellings. The enhanced structuring of the west wall at low F-region altitudes is made possible by the presence of a velocity shear in eastward plasma drift. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1981
- Accession Number
- ADA104554
Entities
People
- Roland T. Tsunoda
Organizations
- SRI International