Irregularities in the Equatorial E Region Over Thumba

Abstract

A rocket‐borne Langmuir probe and plasma‐noise probe have been used to study the ionization irregularities of scale sizes 20 meters to 0.4 meter in the lower equatorial ionosphere over Thumba during the evening twilight of February 2, 1968. lonization irregularities were observed mostly in the height range 97–106 km, 142–155 km and around 170 km. The spectral index n was calculated for a power law of the type E(k) = Akn. In the 100‐km region, irregularities with different spectral indices were found to coexist, indicating the superposition of at least two different spectra. The irregularities with spectral index of −3.0 to −3.5 are probably produced through neutral turbulence, whereas irregularities with spectral index of −1.6 to −2.0 are probably produced by electric fields. The irregularities observed near the rocket apogee are produced by the rocket itself and have a spectral index of +3.0. The actual values of these indices are likely to be more (including sign) than given by the present calculations since the detection efficiency of a Langmuir probe for the irregularities may be size‐dependent.

Temporal and spatial power spectrum studies of numerical simulations of Type II gradient drift irregularities in the equatorial electrojet

“…The computed power laws of the spatial power spectra 1 (k) " k ' , n = 3-4 , for A :9-128 m are in agreement with previous rocket data ( n = 3 + 1; X:1-l5 m , Prakash et al, 1969Prakash et al, , 1970, recent numerical studies ( n 3.5; A :9-75 m , McDonald et al, 1974McDonald et al, , 1975; n = 3 + 1 ;…”

“…-i;;=--:::: This is in agreement with experimental results [ Prakash et al, 1969[ Prakash et al, , 1971[ Prakash et al, , 1972lerkic et al, 1977 for A = 9 m], numerical simulations [ Mcrk~nald et al, 1974[ Mcrk~nald et al, , 1975Ferch and Sudan, 1977] arid dimensional ar~~~ents [O tt and Farley , 1974]. In addition, some evidence is found which suggests that T k ~~~, in agreement with Type II radar observations [Baisley, 1969 ;Farley and Balsley, 1973].…”

“…Tsuda , 1967;Tsuda and Sato, 1967;Rogister , 1972] cannot explain either the vertical Type II radar echoes [Fa n cy and Balsley and Farley, 1973;Fejer et al, 1976] or the density fluctuation amplitudes of 2-5~ observed in rocket experiments [Prakash et al 1969[Prakash et al , 1970[Prakash et al , 1972 for weak electrojet conditions when presumably Typ e II irregulari ties dominate.…”

Naturally enhanced ion-line spectra around the equatorial 150-km region

“…Only a hand full of in-situ measurements have been performed with rockets but the probes did not observe any strong evidence for plasma irregularities (e.g. Prakash et al, 1969).…”

Spectral properties of electrostatic drift wave turbulence in the laboratory and the ionosphere

“…The scatter in spectral indices is large, even within one experiment, and it is recommended that the original papers are consulted to see precisely what result they are being cited for. Note the correction of spectral indices (Prakash et al, 1971) that takes into account a varying filter bandwidth: this reference is predated by others (Prakash et al, 1968(Prakash et al, , 1969, containing an erroneous value for spectral indices. Values for positive spectral indices have been reported by Prakash et al (1971), but these apply only to some unspecified narrow spectral subranges and they are not included in the present summary.…”