Multipower spectrum of small-scale ionospheric turbulence

Abstract

UDC 621.371+533.951We consider the problem of diagnostics of the local structure of small-scale ionospheric turbulence using the multifractal analysis of received signals from the Earth's orbital satellites after the radio sounding of the inhomogeneous ionosphere by these signals. In particular, it is shown that analysis of the multifractal structure of the received-signal amplitude records by the method of multidimensional structural functions allows one to determine the indices of the multipower local spectra of the small-scale ionospheric turbulence, which are inherent in it due to the nonuniform spatial distribution of small-scale fluctuations of the electron number density. It is noted that information on the multipower spectrum of small-scale ionospheric turbulence is not available for the conventional radio scintillation method based on the classical spectral analysis of received signals during the remote radio sounding of the ionosphere. At the same time, the method of multidimensional structural functions is efficient under conditions of actual nonstationarity of the process of scattering of the HF radio waves by the randomly inhomogeneous ionospheric plasma. The method of multidimensional structural functions is used for the multifractal processing of received signals of orbital satellites during special experiments on radio sounding of the midlatitude ionosphere under natural conditions and its modification by high-power HF radio waves. First data on the indices of the multipower local spectra of small-scale ionospheric turbulence are obtained.

Feature of the multifractal structure of small-scale ionospheric turbulence during the solar eclipse of August 1, 2008

“…Such a situation was observed at different ground-based points during the study of multifractal characteristics of the small-scale artificial ionospheric turbulence in the case where the mid-latitude ionosphere heated by powerful high-frequency radio waves from the "Sura" facility [3].…”

“…(1), we calculated the empirical dependences log |∆A(τ )| q ∝ ϕ A (q) log τ for different values of the parameter q. Figure 2 shows the functions ϕ A (q) Then the obtained dependences for the functions ϕ A (q) were used for determining the indices p 3q of the multipower spectra of the local small-scale structure of ionospheric turbulence in accordance with the expression [3] p 3q = 2 + 2α q ,…”

“…When calculating the functions D N (p 3q ), we used Eq. (2) and the well-known formula relating the fractal dimension D N (α q ) of the space occupied by isotropic small-scale irregularities to the fractal dimension D A (α q ) of amplitude fluctuations of the received signals [2,3]:…”

“…The features of the multipower local spectra of a small-scale ionospheric turbulence and the generalized multifractal spectra of small-scale ionospheric turbulence are stipulated by the nonuniform distribution of small-scale fluctuations of the electron number density in space [3]. The inhomogeneous spatial distribution of small-scale fluctuations of the electron density in the ionosphere leads to a special multifractal structure of the amplitude records of the signals received from the satellites (see also [2]).…”

Magnetic zenith effect and some features of the multifractal structure of the small-scale artificial ionospheric turbulence

“…Under such conditions, the process of scattering by HF radio waves in the ionosphere becomes nonstationary, and the classical method of spectral analysis of radio signals is not effective. Hence, for obtaining reliable information on the local structure of the small-scale turbulence when the ionosphere is affected by high-power HF radio waves, one should use a multifractal analysis of received signals, which is based on the measurement of multidimensional structural functions of studied nonstationary random processes [5].…”