Yu. N. Cherkashin

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.

Oblique chirp sounding of the modified ionosphere. Experiment and simulation

We present the results of experimental studies of the influence of artificial ionospheric disturbances on HF signals used for oblique sounding of the disturbed volume. The measurements have been performed by a chirp ionosonde over the path Yoshkar-Ola-“Sura”-niznhy Novgorod with length 234 km. We found the 2F2 mode to disappear (attenuation up to 20 dB) when the ionosphere is influenced by a vertical powerful radiation in the ordinary mode with long (15 min each) heating and pause intervals. Modeling of the observed effect was carried out. The calculations agree well with experimental data if the traveling ionospheric disturbances (TID) with vertical and horizontal scales lz∼20 km and lx∼50 km, respectively, and the relative disturbance of the electron density δN∼0.2–0.3 are amplified (generated) during the ionosphere heating.

Ionosphere plasma holes-modeling and diagnostic

Abstract The influence of ionosphere plasma holes on HF radio wave propagation in approximation of geometrical optics is studied. The results of HF radio wave propagation modeling on routes crossing ionosphere holes are presented. The natural and modeling ionosphere sections are used (we use experimental radiotomography sections on routes: Moscow-Arkhangelsk, Moscow-Murmansk (Russia) and Block Iland-Rabiwhol (USA)). It is shown that characteristics of HF radiowave trajectory (in coordinate: height-latitude) depend on geometrical sizes of hole and the direction, point, angle and frequencies of sounding. It is shown that the asymmetry of electron density distribution results in qualitative and quantitative distinctions of waves trajectories characteristics in dependencies on direction propagation. The characteristic modes of HF radio wave propagation through hole are emphasized — one hop, captured by channel E-F, captured by hole, trapezifrom and so on. The higher interest presents the family of trajectories captured by hole. On estimations, the longest time-delay for different conditions makes up to 23 ms (or range up to 7000 km!). It is possible to say, that the hole in ionosphere can be the trap of HF radiowave. It is discussed conditions of capture and keeping of radio wave by ionospheric hole. The fact, that holes in top ionosphere are long-living and large-scale formations, indicates that disregard of radiowave propagation effects, connected with holes, will result in data distortion or misunderstanding of ionosphere monitoring and control by radiosounding in HF radiowave range.

Modelling of HF wave propagation in the vicinity of quasicritical rays in the disturbed ionosphere

AbstractThe results of experimental studies of the fine structure of a signal in the vicinity of the maximum observed frequency (MOF) on the Khabarovsk—Nizhny Novgorod path of oblique chirp sounding (OCS) are presented. Additional tracks were observed in the region between the high-angle and low-angle rays during magneto-ionospheric disturbances. Under strong disturbances the ionograms were of a spreading type in the vicinity of the MOF. The observed effect was modelled in the presence of travelling ionospheric disturbances (TID) with different parameters. It is shown that the stratification of the high-angle ray into several additional tracks is a maximum for TID with vertical scales

Soliton Propagation in Inhomogeneous Media with Sharp Boundaries

\ell _z \sim {\text{ 20 - 40}}

Nonlocal nonlinear interaction of HF waves with the ionosphere

km whose wave fronts make angles about 0–10° with the horizontal line. The possibilities of using the Pedersen mode as a probing wave for diagnostics of the fine structure of the ionosphere in the vicinity of the F-layer maximum are discussed.

Possibility of the appearance of an anomalous mode in the propagation of short radio waves in the low-latitude ionosphere

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.