K.P. Garmash, S.G. Leus, S.A. Pazura, S.N. Pokhil'ko, and L.F. Chernogor
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Statistical Characteristics of Terrestrial Electromagnetic Field Fluctuations

Magnetometric complex of Kharkov National University has been described briefly. Principal statistical characteristics of variations of H- and D-components of the geomagnetic field in 1999 (duration of the observations was 1488 hours) have been calculated. It has been shown that at averaging on the time interval no less than 10 min statistical distributions of signal amplitudes differ noticeably from normal law. Temporal variations of the sampling root-mean-square deviations and reflect the nature of processes in the geospace (a level of geomagnetic and solar activity, diurnal variations etc.). Spectral and wavelet analysis has confirmed that variations of magnetometric signals H(t) and D(t) besides general information on variations of space weather contain also information on more "subtle" processes in the geospace (amplitude value, pulsation period, pulsation duration etc.).

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V.G. Galushko and G.V. Lytvynenko
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
4, Krasnoznamennaya St., Kharkov 61002, Ukraine
On Applicability of the Isotropic Approximation in the Problem of Frequency-and-Angular Ionospheric Sounding

The paper considers the effect of the geometric field on the accuracy of recovering vertical profiles of the ionospheric electron density by the method of frequency-and-angular sounding. The validity of the isotropic approximation in the problem of frequency-and-angular sounding of the ionosphere (FASI) is analyzed in dependence on the propagation path length and its orientation with respect to the geomagnetic field vector. Recommendations are given as for employing frequency-and-angular dependences for the ordinary and extraordinary magnetoionic components when recovering ionospheric electron density profiles by the FASI technique within the isotropic approximation. The results obtained are validated through numerical calculations for real measured data.

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S.I. Martynenko
V. Karazin National University of Kharkov,
4, Svoboda Sq., Kharkov, 61077, Ukraine
Methods for Remote Sensing of Ionosphere Disturbances in a Strong Mesospheric Electric Field

The approved technique for simultaneous remote sensing of a strong mesospheric electric field (SMEF) intensity and the appearing disturbances of the basic D-region parameters is proposed. The above procedure is based upon the recorded data on the MF radio signals partially reflected from the ionosphere. The model representation of the SMEF source as a current power supply has been used. As an example, we refer to: the height-related profiles of SMEF intensity, the disturbances of effective collision frequency and electron density, relative disturbances of electron temperature, effective electron attachment rate, effective electron-ion recombination coefficient, electron energy loss coefficient per a single collision with a heavy particle, low-frequency plasma conductivity concentrations of positive and negative ions in the lower part of the D-region. The total error in determining the afore-mentioned parameters has been estimated.

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K.P. Garmash, S.V. Lazorenko, S.A. Pazyura, and L.F. Chernogor
V. Karazin National University of Kharkov,
4, Svoboda Sq., Kharkov, 61077, Ukraine
Earth's Magnetic Field Fluctuations during the Severe 1999 Geospace Storm

Using the high-sensitivity fluxmeter magnetometer located in Kharkov V. Karazin National University Radiophysical Observatory (RPO) the unique magnetic storm and the preceding solar flare effects were observed with high temporal resolution. During the storm the magnetometer signals were increased by a factor of up to 50?60 times and a significant enrichment in their spectra was observed. The data processing was performed by applying statistical, spectral and wavelet analyses. The specifics of the geomagnetic field fluctuations are described.

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B.P. Yefimov, K.V. Ilyenko, T.Yu. Yatsenko1, and V.A. Goryashko1
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine,
12, Academician Proskura St., Kharkov 61085, Ukraine

1V. Karazin National University of Kharkov,
4, Svoboda Sq., Kharkov, 61077, Ukraine
Theoretical Model and Experimental Observation of Resonance Generation of Free Electron Laser

A breadboard model is created of free electron laser with homogeneous guiding magnetic field. A theoretical model allowing to explain a number of properties of such device is suggested. It is demonstrated that a resonance amplification of signal power in the range of nonrelativistic and slightly relativistic energies of electrons is in principle possible. Resonance generation conditions connecting initial velocity of electrons with homogeneous guiding magnetic field value are analytically obtained. Comparison of calculation results with results of numerical simulation of electron trajectories has shown a satisfactory fir. Preliminary results are presented of experimental investigations, and a number of resonances in total radiation power predicted by theory are revealed.

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G.P. Kovalenko and S.V. Kolomiets
Sumy National Agrarian University, 160, Kirov St., Sumy, 40021, Ukraine
Periodic Oscillating Modes in Single-Mode Solid-State Lasers

The dynamics of a semiclassical model of a single-mode solid-state laser is studied by the bifurcation method of a cycle initiation. The bifurcation analysis has been carried out for quadratic, cubical and biquadratic dependencies of a Q-switch on the intensity of a photon field. The stability criteria of periodic oscillations which occur as a result of the Hopf bifurcation have been obtained. The intervals of stability for controlling parameters of a Q-switch have been determined.

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