I. V. Krasheninnikov

Investigation by backscatter radar of artificial irregularities produced in ionospheric plasma heating experiments

Abstract The artificial ionospheric turbulence occurs in the ionosphere illuminated by high power HF radio waves. There are a lot of irregularities stretched along the geomagnetic field in this region. The investigation of the artificially disturbed ionospheric region is based on the reception of back scattered signals (BSS) which permits the basic parameters of this region to be estimated and its inhomogeneous structure to be described. Experiments were carried out using ‘Sura’ heating facility in the frequency range of ƒ = 4.7–9 MHz (ordinary mode) with the effective radiated power Peff = 50–70 MW beamed vertically upwards. The most important dynamic and statistical BSS characteristics (the built-up time, the relaxation and autocorrelation times, the BSS amplitude spatial correlation function and power spectra) were measured using probe waves in the frequency range of ƒ p = 1.68−6 MHz that made it possible to obtain the basic parameters of the artificial irregularities. The model representation of a disturbed region in a form of a periodic structure gives a possibity to evaluate the scale of the structure, the whole size of the disturbance and its power and to calculate the main BSS characteristics.

Specific behavior of the radioemission wave field near the maximum usable frequency

The character of a change in the wave field in the frequency range near the maximum usable frequency is analyzed for the model of a simple ionospheric layer. The estimates of the characteristic scale of diffraction damping of the wave field in the frequency range, which are in rather good agreement with the experimental data of LFM or chirp sounding of the ionosphere on two mutually perpendicular paths, have been obtained.

Possibilities of radio sounding of the ionosphere in the decameter range on board a geostationary satellite

It is shown that besides the known method of topside ionospheric sounding (TS) in the decameter range using low-orbit transit satellites, the same frequency range could be used for ionospheric diagnostics, but using geostationary satellites by the method of multifrequency radio transillumination (MRT). The trajectory and energetic features related to the application of this method in the direct problem of transionospheric sounding of the ionosphere are discussed.

Effectiveness of predicting radiowave propagation in the ionosphere based on the IRI-2001 ionospheric model

The standard deviation of predicting radiowave propagation using the IRI-2001 model is estimated based on the data of oblique-incidence sounding on the England-IZMIRAN (∼2500 km) and Cyprus-IZMIRAN (∼2300 km) practically perpendicular paths and vertical radiosounding of the ionosphere at the common point (IZMIRAN) during the period March 2002–2007. The observational period covers a wide range of solar activity values: the sunspot number R varied from 112 at a maximum (2002) to 4.8 at a minimum (2007). The results of an analysis of the complex experimental data, which agree with their description by the IRI-2001 model, completed with the calculations of the electron collision frequency, are presented.

IRI model in the problem of predicting ionospheric radio-wave propagation under conditions of high solar activity

The paper presents the results of an analysis of the correspondence between model representations the monthly mean diurnal dependences of critical frequency and vertical profiles of plasma frequency at local noon at IZMIRAN station for the middle months of the four seasons of 2014, the year of the maximum solar activity in the current 24th cycle. It is shown that in general the IRI model reliably describes the daily variation of foF2, and the smallest discrepancy is achieved when its basic input parameter is given by the ionospheric index of solar activity IG12. An exception is April, for which there is a fundamental discrepancy with the model both in the daily variation of the critical frequency foF2 and in the Ne(h)-profile for local noon time. For this month, the inadequacy in the model representation of the vertical distribution of the electron density turned out to be very significant in the calculation of the MUF: the relative error can reach 20%. The simulation results are confirmed by data from oblique-incidence ionospheric radio sounding.

Trapping of sensing radio waves in an artificial large-scale ionospheric cavity

The results of phenomenological analysis of data from oblique chirp sounding of the ionosphere in a 2007 heating experiment with possible recording of the effect of trapping sounding-radiation in an artificial ionospheric cavity and spotlighting it in the near (over the Earth’s surface) zone of the Sura facility are presented. The physical aspects of forming an additional trace on ionograms of oblique radio-sounding of the perturbed region of the ionosphere are discussed.

Analysis of the wave field mode structure on the Moscow–Akademik Vernadskii Antarctic station superlong path

The Doppler spectrum of an exact time harmonic radio signal for the frequency of 5 MHz on the Moscow–Akademik Vernadskii Ukrainian Antarctic station radio path in November 2002, which had two clearly defined spectral groups, has been analyzed. It is shown that an insignificant frequency shift corresponds to a standard radio wave propagation in a short direct direction. The assumption that the formation of a spectral group with a considerable frequency shift is refraction is theoretically justified based on a simplified model of the morning terminator transition region. The field strength, signal-to-noise ratio, and Doppler frequency shift obtained in the scope of the IRI-2001 extended global ionospheric model for the classical radio wave propagation modes on a superlong radio path are estimated.