Intensity scintillation parameters for characterizing transionospheric radio signals

[1] Previous ground observations have revealed a correlation that exists between equatorial plasma bubbles, evening equatorial ionization anomaly (EIA), and prereversal E Â B drift velocity using latitudinal arrays of ionospheric sounders, such as in the Indian and American regions. Besides the ground measurements, the space-based observations also provide a convenient way to study the global-scale variations. On the basis of in situ data collected from DMSP, ROCSAT-1, and CHAMP satellites, we investigated the correlation of seasonal/longitudinal variations of plasma bubble (PB) occurrence, evening EIA, and prereversal E Â B drifts on magnetically quiet days during the solar maximum years (2000)(2001)(2002). In general, the observational results provide consistent evidences that the large-scale variations in seasonal/longitudinal distribution of evening EIA and PB occurrence rates are well-correlated with the observed evening prereversal E Â B drifts and that some of the small-scale longitudinal variations (such as wave number-4 structure during equinox) of evening EIA exist before the occurrence of the prereversal enhancement and coincide with the daytime equatorial electrojet. In such cases, the small-scale longitudinal variation of PB occurrence rates may result from the evening EIA small-scale longitudinal structures. The evening prereversal E Â B drifts, together with the longitudinal variations of evening EIA, are assumed to play a role in determining the longitudinal variations of equatorial and low-latitude PB occurrence rates.

Section: Resultsmentioning

confidence: 99%

Correlative study of plasma bubbles, evening equatorial ionization anomaly, and equatorial prereversal E × B drifts at solar maximum

Ning

Liu

et al. 2008

“…This universal parameter is the S 4 index determined under weak scatter conditions, which would be applicable for a sufficienfiy high signal frequency. Rino and Liu [1982] demonstrated that for irregularities with a power law spectrum having an outer scale much larger than the Fresnel radius, the S 4 index in the weak scatter limit, denoted in the literature by S40, incorporates the irregularity parameters including the strength of the irregularities in such a manner that the level of scintillation on another frequency can be characterized by S40 itself without specifying the propagation geometry and the irregularity parameters. In the present calculations, S4(140) may be equated to S40 as long as S4(140) < 0.3, a criterion for the weak scatter regime used by Rino and Liu [1982].…”

Section: S 4 Index From the Fourth-moment Equationmentioning

confidence: 99%

Signal frequency dependence of ionospheric amplitude scintillations

Bhattacharyya¹,

Rastogi²,

Yeh³

1990

The S4 index, which is a measure of the strength of amplitude scintillations, is assumed to vary with signal frequency f according to S4 ∝ f−n, and the frequency exponent n is derived from observed equatorial amplitude scintillations on 40‐ and 140‐MHz signals. A large data base has been used to study the variation of this exponent n(40/140) with the S4 index on the 140‐MHz signal for both daytime and nighttime scintillation events. Although the equatorial E and F region irregularities, which cause the observed scintillation events, have different characteristics, the variation of n(40/140) with S4(140) is found to be almost universal. Theoretical computation of n(40/140) for different values of the irregularity parameters yields results which are in good agreement with these observations.

“…Buckley [1975] used this method earlier to verify theoretical results derived by using Taylor series expansions of the phase structure function and the Gaussian phase screen theory. Our approach is motivated by more recent theoretical work [Rino, 1979b;Rino and Liu, 1982] that uses asymptotic approximations that are better suited for typical transionospheric propagation conditions.…”

Section: Pothesismentioning

confidence: 99%

“…Verifying that this limit exists as long as 1 < p < 5 is straightforward; moreover, a well-defined limiting form for (I)z(K) itself exists when R approaches zero. In fact, any parameter that characterizes the intensity statistics consistently over the full range of admissible lo and 15 values must also have a well-defined limit as R approaches zero [Rino and Liu, 1982]. The R = 0 results are referred to as the asymptotic theory or the "turbulence parameter" approximation.…”

Section: Theorymentioning

confidence: 99%

Numerical simulations of intensity scintillation using the power law phase screen model

Rino¹,

Owen²

1984

Self Cite

Simulations of radio wave scintillation in power law media were performed to study the structure of the intensity and phase spectra when the Fresnel radius is much smaller than the outer scale or the low‐frequency limit of the power law regime in the in situ irregularity spectrum. The results verify the critical dependence of intensity scintillation on the power law index as predicted by both asymptotic and more refined theoretical computations. Because of more recent findings, the scintillation characteristics of propagation in media characterized by a two‐component power law were also investigated. The results reconcile the interpretation of scintillation data from the Wideband satellite which showed a shallowly sloped power law phase spectrum with more recent intensity scintillation data.