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Backscatter Measurements of 11-cm Equatorial Spread-F Irregularities.

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Topical rept. no. 5, 1 Oct-1 Nov 79,

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An important objective of the Defense Nuclear Agency is to understand the physical processes that control the dissipation of turbulent structure in plasmas. Such turbulent structures occur as a consequence of high-altitude nuclear events as well as in the natural, disturbed equatorial ionosphere. Analysis and understanding of those processes in the nighttime equatorial F-region ionosphere that are analogous to those found in the nuclear environment can lead to an intelligent extrapolation of equatorial findings to the nuclear case. In the equtaorial F-region ionosphere, the turbulent cascade process had been found previously to extend from irregularity spatial wavelengths longer than tens of kilometers down to wavelengths as short as 36 cm. To investigate the small-scale regime of wavelengths less than 36 cm, a radar backscatter experiment was conducted in the Kwajalein Atoll, Marshall Islands using a frequency that corresponds to an irregularity wavelength of 11 cm. The first observations of radar backscatter from 11-cm equatorial field-aligned irregularities FAI are described. These measurements extend the spatial wavelength regime of F-region FAI to lengths that approach both the electron gyroradius and the Debye length. Agreement of these results with the theory of high-frequency drift waves suggests that these observations may be unique to the equatorial ionosphere. That is, the requirement for low electron densities that the theory calls for may preclude the existence of 11-cm FAI elsewhere in the F-region ionosphere, except in equatorial plasma bubbles. Author

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  • Atmospheric Physics
  • Active and Passive Radar Detection and Equipment
  • Radiofrequency Wave Propagation

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