Simultaneous rocket‐borne beacon and in situ measurements of equatorial spread <i>F</i>—Intermediate wavelength results

Abstract

A high‐performance rocket carrying a four‐frequency, phase‐coherent beacon and full complement of in situ diagnostic instrumentation was launched into active equatorial spread F on July 17, 1979. In this paper we report the results of spectrally analyzing the beacon phase‐scintillation and Langmuir probe data. By using simultaneous backscatter data from the Altair radar we were able to establish that the scintillation develops in high‐density regions adjacent to the prominent plume structures and associated depletions. In these high‐density regions the in situ spectra show a pronounced change in the power law slope near a spatial wavelength of 500 m. Larger scale structures admit a systematically varying power law index that is generally less than 2, in good agreement with a large body of Wideband satellite data and recently analyzed Atmospheric Explorer E data. Smaller‐scale structures admit a spectral index much larger than 2. A single, overall power law near k −2 was found only in low‐density regions that did not contribute significantly to the scintillation. The results presented here and in a companion paper suggest that refinements in the current theories of equatorial spread F near and above the F region peak are needed.