STEEPENED STRUCTURES IN EQUATORIAL SPREAD-F .1. NEW OBSERVATIONS

Sounding rocket data from the 1990 CRRES/EQUIS equatorial spread F campaign on Kwajalein Atoll are presented. Two Terrier Malamute sounding rockets were launched into active spread F conditions on July 30 and August 2, respectively, and achieved apogee slightly below 500 km, just above the F peak. Plasma frequency probes aboard both rockets showed that the unstable nighttime F region is characterized by propagating steepened structures. Power density spectra for the structures typically exhibit two regions that obey k-n scaling, where n is approximately equal to 2 at wavelengths greater than 80-100 m and approximately equal to 5 at shorter wavelengths. These spectral indices are quite variable, and the long-wavelength spectral index in particular seems to decrease with increasing amplitude of density fluctuations. The rocket payloads also measured vector electric fields in the plane perpendicular to B over wavelengths ranging from over 60 km to less than 6 m. Both vector components of the perpendicular electric field are proportional to deltan/n at wavelengths longer than 300 m but assume a Boltzmann relationship (with ]deltaE\2 is similar to k2\deltan/n\2) at smaller scales. The perturbed zonal electric field, deltaE(x), dominates the vertical field, deltaE(z), at long wavelengths, but the situation is reversed at smaller scales.