Simultaneous rocket‐borne beacon and in situ measurements of equatorial spread F—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.

Some new features of electron density irregularities over SHAR during strong spread F

“…These spectral index values, though slightly higher than those reported by Rino et al (1981), can be interpreted in terms of GRT instability. Thus the intermediate irregularities, observed over SHAR, appear to be generated through GRT instability and the dominant contribution to the growth is by gradient drift instability and not by RT instability.…”

“…Woodman and LaHoz (1976) ®rst identi®ed valley region irregularities below the main plumes in the RTI radar maps obtained from Jicamarca. Vickrey et al (1984) studied electron density irregularities observed in the F region valley, which were obtained from ®xed bias LP¯own on two rockets launched from Natal, Brazil (Kelley et al, 1976(Kelley et al, , 1979Costa and Kelley, 1978) and from Kwajalein Atoll (Szuszczewicz et al, 1980Rino et al, 1981;Kelley et al, 1982b). During these twō ights quasi-sinusoidal¯uctuations in the F region valley (170 to 200 km) were observed where the local zero order vertical plasma density gradient nearly vanishes.…”

“…Costa and Kelley (1978) found that sharp density gradients (gradient scale length, L < 100 m) could de-stabilize collisional drift waves. Rino et al (1981) discussed the ®xed-bias Langmuir probe derived electron density power spectra, obtained from Plumex-I rocket, launched from Kwajalein Atoll (9.4°N, 167.45°E). A fully developed spread F in decay phase was encountered during this experiment.…”

Spectral features of E- and F-region plasma irregularities as observed by rocket-borne electron density probes from Brazil

“…For the same flight Costa & Kelley (1978) found a power law of the type k n with spectral index n = -2.0 for the steep coherent density structures of scale size (scale size λ = 2π/k where k is the wave number) in the range between 10 km and 10 m (k in the range between 0.628 km -1 and 628 km -1 ) in the bottom side F-region. Rino et al (1981) found that for electron density irregularities with scale sizes between 5 km and 500 m (k between 1.257 km -1 and 12.57 km -1 ) the spectral index n ranged between -1.2 and -2.5 and for irregularities with scale sizes between 50 m and 500 m (k between 125.7 km -1 and 12.57 km -1 ) the n value was between -2.3 and -3.4 indicating steeper spectra for altitudes below 370 km. For higher altitudes the observed n values ranged between -1.2 and -2.6.…”

Equatorial F-region irregularities generated by the Rayleigh-Taylor instability mechanism: rocket observations from Brazil

“…Several rocket campaigns have been reported for studying the phenomenon of spread-F in the American region (Kelley et al, 1976;Morse et al, 1977;Rino et al, 1981;Szuszczewicz et al, 1981;Kelley et al, 1982;Hysell et al, 1994) and a few campaigns in the Indian zone Prakash et al, 1991;Sinha et al, 1999;. Kelley et al (1982) reported that at altitudes above about 280 km the electron density spectrum varied as k −5 while the electric field fluctuations showed a power law dependence of k −3 .…”