卷 58, 编号 8 (2016)

We study the dynamics of the geomagnetic-pulsation spectra at unusually high frequencies (including the frequencies exceeding the Schumann resonance frequency 8 Hz), which were detected for the first time at the Novaya Zhizn’ midlatitude station (the McIlwain parameter L = 2.6) at the time of a strong magnetic storm on November 07–14, 2004. To interpret the observed pulsation frequencies, we used the data from the NOAA low-orbit satellites which recorded localized precipitations of energetic protons (with energies of 30 to 80 keV) and calculations of the singlepass cyclotron amplification of electromagnetic ion–cyclotron waves. Amplitude and polarization characteristics of the radiation spectra at frequencies of up to 15 Hz at the Novaya Zhizn’ and Lovozero stations (L = 5.2) are compared. It is shown that the magnetic field oscillations in the frequency range 7–15 Hz correlate with proton precipitations and proton auroras at geomagnetic latitudes 50°–57° (L = 2.42–3.37). It is also shown that for a high anisotropy of the pitch-angle distribution of the ring-current protons at such low geomagnetic latitudes, the frequency spectrum of observed high-frequency radiation agrees well with the calculated location of the maximum of the single-pass cyclotron amplification of electromagnetic ion–cyclotron waves. Analysis of the data and calculation results has led to the conclusion that inherently the recorded signals are a high-frequency counterpart of the Pc1 pulsations and are due to the generation of ion–cyclotron waves in the magnetosphere at unusually low latitudes, which are probably stipulated by the shift of the plasma pause to these latitudes during a strong magnetic storm.

We study the possibility of determining the inherent hydrooptical characteristics of water using the underwater-vision means. Analytical models of the instantaneous and accumulated images of the underwater solar path, which is formed by direct, singly scattered, and multiply scattered light, are proposed. The optical depths at which the contribution of the water-scattered light to the apparent radiance of the surface becomes predominant are estimated using numerical simulation. Algorithms for reconstructing the water scattering and attenuation coefficients from the accumulated image of the underwater solar path are developed. The results of the algorithm evaluation using the data of a full-scale experiment are presented.

We study the possibility to develop a high-power free-electron maser amplifier with an operating frequency of 30 GHz to be used in particle acceleration experiments. Various operation regimes are considered, which are capable of ensuring a wide instantaneous amplification band with a high electron efficiency. It is shown that it is possible to achieve a gain ratio of more than 25 dB and an output power of 20 MW in a frequency band with a width of up to 20% of the operating frequency in the so-called dispersion curve contact regime by using a moderately relativistic electron beam formed by the LIU-3000 induction accelerator in an undulator with a regular winding. Application of the profiled undulator allows one to achieve a radiation power of up to 50 MW in a band having a width of more than 50% of the operating frequency in the regime of non-resonant trapping and deceleration of particles.

The absolute error of determining the center frequency of the molecule spectral line during a single measurement, which is obtained by fitting the line shape to the model profile, is usually significantly smaller than the statistical spread in the frequencies of the repeated measurements. We discuss the possible causes of the systematic errors leading to an increase in the uncertainty of measurements of the line-center frequency. For an example of the multiple spectral measurements of the rotational transitions of the¹⁶O¹²C³²S molecule in the millimeter- and submillimeter-wave ranges (with a frequency of up to 522 GHz), by the Lamb-dip method, we determine the absolute error of the performed measurements, which amounts to 0.4 kHz. New precision values of the center frequencies of the rotational transitions of the¹⁶O¹²C³²S molecule and more accurate values of the rotational constants, which are calculated using the measured frequencies, are presented.