arXiv subjects

A. S. Potapov

Publications and source records attributed to A. S. Potapov.

8 recordsLinked to original sources

arXiv2026

The Pc1 geomagnetic pulsations in light of the Cepheid theory

It has been 90 years since the discovery of geomagnetic pulsations in the Pc1 range (0.2-5 Hz), widely known as pearls. In the second half of the last century, the concept of pearls as multiple echoes of a wave packet that propagates along the lines of the geomagnetic field, periodically reflecting off the ionosphere at magnetically conjugate points emerged. This paper proposes an alternative interpretation of the pearls. It is assumed that high above the Earth in the narrow equatorial zone of the outer radiation belt there is a pulsed generator of ion-cyclotron waves. The generator excites a discrete sequence of wave packets, which are recorded in the magnetosphere and on the Earth's surface as a series of pearls. The generator is a Q-modulated ion cyclotron resonator with active filling. The presence of opacity domains adjacent to the resonator's end faces is reminiscent of the opacity layer in the atmosphere of a Cepheid. This association was strengthened by the fact that in both cases the formation of opaque layers is associated with the presence in the medium of ions with different charge-to-mass ratios. Based on this association, the idea of a ponderomotive valve arose, periodically changing the width of the opacity domains, thereby forming a periodic sequence of pearls. The ponderomotive valve in pearl theory is analogous to the Eddington valve in Cepheid theory.

physics.geo-ph↗

arXiv2024

On ponderomotive metallization of magnetospheric plasma

The problem of ponderomotive separation of ions with different charge-to-mass ratios under the influence of Alfven waves, which permanently exist in the magnetosphere in the form of geomagnetic pulsations, is posed. Formulas are derived for partial ponderomotive forces acting on light and heavy (metal) ions. In the quasi-hydrodynamic approximation, it was found that the Clarke number, which characterizes the metallicity of the plasma, is maximum at the minimum of the magnetic field on the field line along which the Alfvén wave propagates. Key words: ponderomotive forces, Alfvén waves, heavy ions, Clarke number.

physics.plasm-ph↗

arXiv2022

Alfvén waves: To the 80th anniversary of discovery

The paper is dedicated to the anniversary of the discovery of Alfvén waves. The concept of Alfvén waves has played an outstanding role in the formation and development of cosmical electrodynamics. A distinctive feature of Alfvén waves is that at each point in space the group velocity vector and the external magnetic field vector are collinear to each other. As a result, Alfvén waves can carry momentum, energy, and information over long distances. We briefly describe two Alfvén resonators, one of which is formed in the ionosphere, and the second presumably exists in the Earth's radiation belt. The existence of an ionospheric resonator is justified theoretically and confirmed by numerous observations. The second resonator is located between reflection points located high above the Earth symmetrically with respect to the plane of the geomagnetic equator. Keywords: Alfvén velocity, dispersion law, group velocity, geometric optics, heavy ions.

physics.geo-ph↗

arXiv2021

Discrete Spectrum of ULF Oscillations of the Ionosphere

This work relates to the field of ultra-low-frequency (ULF) spectroscopy of near-Earth plasma. Our attention is focused on the Alfvén ionospheric resonator (IAR), the spectrum of which is a series of discrete lines. The aim of the study is to experimentally verify a well-defined theoretical prediction. Within the framework of an idealized resonator model, a hypothesis about the relationship between the frequencies of spectral lines has been formulated. To test the hypothesis, observations of ULF oscillations at the mid-latitude Mondy observatory were used. The result of the analysis confirmed the hypothesis that odd harmonics of the IAR discrete spectrum are observed on the Earth's surface. Key words: electromagnetic oscillations, Alfvén waves, ionospheric Alfvén resonator, ultra-low-frequency spectroscopy.

physics.geo-ph↗

arXiv2021

A Paradox of Whistling Atmospherics

Analyzing paradoxes is interesting and instructive. Sometimes the analysis leads to non-trivial results. This methodological note sets out a paradox arising in the theory of propagation of electromagnetic waves in moving plasmas. The paradox is interesting in itself, and, generally speaking, it should be taken into account when analyzing geoelectromagnetic waves. The paradox is as follows: contrary to expectations, the group velocity of the waves is the same in the comoving and laboratory frames of reference. The condition for the appearance of the paradox is the quadratic dependence of the frequency on the wave number. A paradoxical property manifests itself in the theory of the propagation of radio waves (in particular, whistling atmospherics), Langmuir waves and Alfvén waves. From a cognitive point of view, it is interesting that the paradox can be traced in relation to de Broglie waves. An explanation of the paradox is proposed. Keywords: group velocity, moving plasma, Doppler Effect, dispersion, longitudinal waves, transverse waves.

physics.geo-ph↗

arXiv2020

Distillation of neural network models for detection and description of key points of images

Image matching and classification methods, as well as synchronous location and mapping, are widely used on embedded and mobile devices. Their most resource-intensive part is the detection and description of the key points of the images. And if the classical methods of detecting and describing key points can be executed in real time on mobile devices, then for modern neural network methods with the best quality, such use is difficult. Thus, it is important to increase the speed of neural network models for the detection and description of key points. The subject of research is distillation as one of the methods for reducing neural network models. The aim of thestudy is to obtain a more compact model of detection and description of key points, as well as a description of the procedure for obtaining this model. A method for the distillation of neural networks for the task of detecting and describing key points was tested. The objective function and training parameters that provide the best results in the framework of the study are proposed. A new data set has been introduced for testing key point detection methods and a new quality indicator of the allocated key points and their corresponding local features. As a result of training in the described way, the new model, with the same number of parameters, showed greater accuracy in comparing key points than the original model. A new model with a significantly smaller number of parameters shows the accuracy of point matching close to the accuracy of the original model.

cs.CV↗

arXiv2018

Do 5-minute oscillations of the Sun affect the magnetosphere and lithosphere of the Earth?

In this paper, we analyzed a number of problems that are relevant for the physics of solar-terrestrial relationships and the dynamics of geospheres. It is shown that permanent 5-minute oscillations of the photosphere, well known in helioseismology, probably influence regime of the ultra low frequency (ULF) geoelectromagnetic waves. We detected maxima at a period close to 5 min in the spectra of the ULF waves of SE, BMP and Pc5 types. As for the question of the influence of 5-minute oscillations of the photosphere on geoseismicity, the answer is negative. This could be foreseen in advance, but the very formulation of the question led unexpectedly to a turn of the topic and gave us an opportunity to discuss the problem of the hidden periodicity of natural processes synchronized by the world clock. The article was written during the authors' visit to the GO Borok IPE RAS in the summer of 2018. Keywords: gelioseismology, interplanetary plasma, Alfvén waves, Doppler effect, ultra-low-frequency oscillations, earthquakes, thunderstorms, human impact.

physics.geo-ph↗

arXiv2014

On Permanent and Sporadic Oscillations of the Magnetosphere

In this paper we investigate the impact of permanent oscillations Pc3 on the excitation of sporadic oscillations Pi2 ( their periods are 10-45 and 40-150 s, respectively ). The hypothesis is formulated that Pc3 oscillations originating in front of the magnetosphere penetrate into the geomagnetic tail, cause a local depression in the current in the neutral sheet, and under favorable conditions stimulate a tearing instability. This leads to reconnection of magnetic field lines and an explosive release of magnetic energy stored in the tail. As a result, a substorm breaks up, with sporadic pulsations Pi2 as an important element of this process. It is expected from theoretical estimates and kinematic considerations that the higher the Pc3 frequency, the earlier the Pi2 trains start. We test this prediction using observational data from satellite measurements of the interplanetary magnetic field and on-ground magnetic measurements. The results confirm the theoretical expectation. Additional routes are proposed to theoretically and experimentally test the hypothesis.

physics.space-ph↗