Some features of the fractal structure of the developed small-scale ionospheric turbulence

Myasnikov

et al. 2008

Self Cite

We show the results of the first experimental studies of the multifractal structure of the developed artificial ionospheric turbulence. As a result of the special multifractal analysis of the recorded amplitudes of signals from the orbital satellites, which were obtained during the experiments on radio tomography of the irregularities excited in the ionosphere by the powerful mid-latitude heating facility "Sura," it is found that the characteristic multifractal structure of these records is caused by the nonuniform spatial distribution of the small-scale fluctuations of the electron number density in the artificial irregularities of the ionospheric plasma. Comparative analysis is performed for the multifractal spectra of fluctuations of both the amplitudes and energies of signals received from the orbital satellites upon radio transmission probing of the region of artificial ionospheric turbulence by these signals at three observation points located near the "Sura" heating facility and spaced apart to a distance of about 100-150 km.

Section: Experiments Layout and Measurement Resultsmentioning

confidence: 99%

Section: Experiments Layout and Measurement Resultsmentioning

confidence: 99%

Section: Experiments Layout and Measurement Resultsmentioning

confidence: 99%

Section: Discussion Of Experimental Resultsmentioning

confidence: 99%

Section: Discussion Of Experimental Resultsmentioning

confidence: 99%

See 3 more Smart Citations

Fractal structure of artificial ionospheric turbulence

Myasnikov

et al. 2008

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Multifractal Structure of Intermittency in a Developed Ionospheric Turbulence

Rakhlin

2008

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We present the results of studying the multifractal structure of intermittency in a developed ionospheric turbulence during special experiments on radio-raying of the midlatitude ionosphere by signals from orbital satellites in [2005][2006]. It is shown, in particular, that the determination of multidimensional structural functions of the energy fluctuations of received signals permits one to obtain the necessary information on multifractal spectra of the studied process of radio-wave scattering in the ionosphere. Experimental data on multifractal spectra of slow fluctuations in the received-signal energy under conditions of a developed small-scale turbulence are compared with the existing concept of the radio-wave scattering within the framework of the statistical theory of radio-wave propagation in the ionosphere. It is inferred that under conditions of a developed ionospheric turbulence, the multifractal structure of the intermittency of slow fluctuations in the received-signal energy is a consequence of the intermittency of small-scale fluctuations in the electron number density of the ionospheric plasma on relatively large spatial scales of about several ten kilometers.Some structural features of a developed small-scale ionospheric turbulence (SSIT) were explored during our experiments on radio-raying of the midlatitude ionosphere by signals from orbital satellites in 2005-2006 [1]. Emphasis was placed on a study of multidimensional structural functions of order q [∆A(τ )] q for fast amplitude fluctuations A(t) of the signals received on the Earth. This yielded important information on the local structure of the developed ionospheric turbulence which was inaccessible in the conventional remote studies of the ionosphere using the classical radio-scintillation technique [1-3]. Developed ionospheric turbulence requires the presence of a broad spectrum of inhomogeneities of the medium, whose statistical characteristics satisfy a certain scaling law. Earlier, the statistical process of ionospheric scattering of radio waves was assumed uniform, and statistical moments of the second order were used for its description [3]. Such a process is characterized by a well-defined chaotic structure of fast fluctuations in the received-signal amplitude with, as was generally assumed, uniform behavior of the scintillations [3]. Actually, the scattering of radio waves by small-scale irregularities of the ionospheric electron number density even in the case of a developed SSIT is not uniform, and the fractal method (see [2] for more detail) should be used for its correct description. In this experiment, as before, we use records of the received satellite signals with quasihomogeneous form of scintillations, but now we analyze multidimensional structural functions of the amplitude fluctuations of received signals [1]. However, by virtue of their dynamic properties, multidimensional structural functions of the amplitude fluctuations cannot be used for a sufficiently complete study of the intermittency (irregularity) of the amplit...

On the Problem of True Values of the Spectrum Indices for Small-scale Ionospheric Turbulence

Rakhlin

2008

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We consider the problem of obtaining reliable values of the local-spectrum indices of the electron number density fluctuations for small-scale ionospheric turbulence. It is shown that the use of a multifractal analysis in combination with the synchronous correlation processing of the received signals in the experiments on remote radio sounding of the ionosphere by satellite signals permits one to solve the posed problem. In this case, the true values of the local-spectrum indices of smallscale ionospheric turbulence, which are measured in such specialized experiments under natural conditions and during modification of the ionosphere by high-power HF radio emission, can differ notably from their standard values obtained within the framework of the classical method of radio scintillations, in which only correlation processing of the data is used.In theoretical paper [1], we considered the problem of true values of the local-spectrum indices of the electron number density fluctuation for small-scale ionospheric turbulence. In particular, it was shown that the classical multifractal analysis of weak amplitude fluctuations of the received signals during remote radio sounding of the ionosphere from the satellites in combination with the conventional correlation processing yields the necessary information on the fractal dimension D A of samples of the signal-amplitude fluctuations and the corresponding index p A of the amplitude fluctuation spectra. In turn, knowledge of the parameters D A and p A makes it possible to determine the true values of the local-spectrum indices of the electron number density fluctuations for small-scale ionospheric turbulence and find the values of the fractal dimension of the space occupied by small-scale irregularities of these fractal structures in the ionosphere.However, during the first specialized experiments on radio sounding of the midlatitude ionosphere by signals of orbital satellites in 2005−2006, it was found that the structure of developed ionospheric turbulence cannot always be described in terms of the generally accepted multifractal model. In the analysis of the results of the measurements performed in the course of those experiments, it was established that for the structural functions of fluctuations of the received-signal amplitude A(t) and a small temporal separation τ , the following relationship is valid [2,3]:where T is the temporal range of the analyzed sample of the signal amplitude, ϕ A (q) is the scaling index during approximation of the experimentally measured qth-order structural functions of amplitude fluctuations, and D A (α q ) is the fractal dimension of amplitude fluctuations of the received signals, which is determined on the set q of structural functions from the parametric dependence [2, 3] D A (α q ) = 1 ± [α q q − ϕ A (q)], α q = dϕ A (q)/dq.