Том 61, № 8-9 (2019)

We consider typical approaches to modeling of geodynamo processes in the liquid core of the Earth. Some features of magnetohydrodynamic turbulence under rapid rotation conditions are presented. On the example of net helicities, it is shown how rapid rotation facilitates the generation of a large-scale magnetic field and how the mechanism of the inverse effect of the magnetic field on the flow under geostrophy conditions is implemented. The arguments, based on the symmetry properties, in favor of the existence of a connection between the rapid rotation and the inversion frequency, as well as a number of other large-scale characteristics of the dynamo system, are given.

We study the convective diffusion of passive admixtures in the course of forced fluid filtration through a porous medium with frozen random inhomogeneities of macroscopic parameters. During the fluid filtration, the parameter inhomogeneities lead to spatially irregular flows and are responsible for dispersion of the fluid particles, which causes convective diffusion that is additional to molecular diffusion. In contrast to the molecular diffusion, this diffusion is anisotropic and directly proportional to the filtration flow velocity. We consider the inhomogeneities of both permeability and porosity of the medium and report on analytical results for the most common options of their statistical properties. It was assumed that the inhomogeneities are relatively small and their autocorrelation function decays with the distance r not slower than 1/r^β, where β > 1. Direct numerical simulation for different cases confirmed the validity of the restrictions we adopted and the correctness of the analytical findings.

The paper discusses the features of the previously published method of the Bayesian statistical evaluation of simultaneous satellite measurements of the minor species OH, HO₂, and O₃ at the mesospheric altitudes. These features are due to the introduction of a priori constraints on true concentration values (masked by measurement noise), which are determined by the condition of photochemical equilibrium of the species. The method is based on the probabilistic view of the satellite measurement process where the true concentrations of OH, HO₂, and O₃ are considered as random variables. In such a technique, we construct the a posteriori probability density of these variables and compare its statistical characteristics with the initial measurement data. It is shown that there is ambiguity in the construction of the a posteriori probability density of OH, HO₂, and O₃, which is due to the different ways of limiting transition from the three-dimensional probability distribution to the surface one. The ambiguity significantly affects the statistical means and leads to an inevitable systematic error. We present the main options for choosing the probability density, depending on the type of the transition. To estimate the systematic error, we tested the method by using artificial noisy model data on OH, HO₂, and O₃ that simulate perfect (unbiased) measurements. It is shown that choosing a patch transition leads to the least systematic error. Applying the method to MLS/Aura data of July 2005 confirmed the conclusion made earlier that the satellite measurements of the HO₂ concentration have a significant bias greatly exceeding the systematic error of the method. This leads, in particular, to a significant error in the localization of the concentration maximum of this component at the mesospheric altitudes.

We consider nanosecond subterahertz waveguide switches based on a 3D resonator with an active element made of a semiconductor, whose conductivity is controlled by a laser. Recently discovered possibilities to use these switches to obtain pulses with very long durations (up to tens of seconds) along with nanosecond pulses in one and the same device prototype are discussed. Switching with no distortion of the coherent radiation of promising subterahertz gyrotrons, which have powers of about several watts and pulse durations of up to ten seconds are demonstrated experimentally. The theoretical estimate of limiting powers of the switched subterahertz waves, which was proposed earlier, is confirmed and generalized. For this purpose, we perform a measurement of the powers by reducing it to a trivial measurement of the power of radiation of an industrial IR laser. Improvement of the resonance characteristics of the developed switch after switching several sequential long subterahertz pulses has been revealed. Most probably, it is due to “burning-off” of microscopic manufacturing defects and the approach of the actual frequency-amplitude characteristic to the calculated one. It has been predicted theoretically and partially confirmed experimentally that it is not possible to disable the switch being in the fundamental equilibrium state upon switching arbitrarily high powers of subteraheratz waves near the resonance band.

We study the statistical moments of the soliton gas (mean field, variance, skewness, and kurtosis), which is described within the framework of the Gardner equation with negative cubic nonlinearity. The influence of the limiting (thick or table-like) soliton on the statistical moments of the soliton gas is considered. It is shown to be substantial if the thick-soliton intensity is comparable with that of the moderate-amplitude solitons.

We have developed a method for deriving systems of closed equations for the dynamics of order parameters in the ensembles of phase oscillators. The Ott–Antonsen equation for the complex order parameter is a particular case of such equations. The simplest nontrivial extension of the Ott–Antonsen equation corresponds to two-bunch states of the ensemble. Based on the equations obtained, we study the dynamics of multi-bunch chimera states in coupled Kuramoto–Sakaguchi ensembles. We show an increase in the dimensionality of the system dynamics for two-bunch chimeras in the case of identical phase elements and a transition to one-bunch “Abrams chimeras” for imperfect identity (in the latter case, the one-bunch chimeras become attractive).

We study the structure and properties of the chimera states in the ensembles of chaotic oscillators with nonlocal coupling. It is shown that the phase and amplitude chimera states in the ensembles of chaotic oscillators with nonhyperbolic and hyperbolic attractors can be obtained using the models in the forms of two-dimensional Hénon and Lozi maps. The mechanisms of birth, the structure, and the lifetime of the phase and amplitude chimeras and the regime of solitary states are studied. The chimera states in two coupled ensembles of chaotic maps are considered. The possibility of realizing a new type of the chimera structure, namely, the chimera consisting of the solitary states is demonstrated. The effects of the external and mutual synchronizations of the chimera states are described by an example of two coupled ensembles of logistic maps with nonlocal coupling. A qualitative analogy of the obtained results with the classical effect of synchronization of periodic self-sustained oscillations is discussed.

In this work, we experimentally study the heart rate variability, photoplethysmograms, and electroencephalograms of healthy subjects in the course of active experiments with respiration, whose rate varied according to a known law. On the basis of the experimentally measured signals of the heart rate variability, photoplethysmograms, and electroencephalograms, it is shown that the low-frequency regulation processes with frequencies below 1 Hz interact with each other and are significantly influenced by the respiration process. The obtained results are indicative of the presence of several vegetative-regulation centers whose activity is manifested in the low-frequency dynamics of the signals of the heart rate variability, photoplethysmograms, and electroencephalograms.