Searcharxiv⌕ Search

arXiv subjects

A. A. Soloviev

Publications and source records attributed to A. A. Soloviev.

9 recordsLinked to original sources
arXiv2025

Magnetic stagnation of two counterstreaming plasma jets induced by intense laser

Experiments with interacting high-velocity flows of laser plasma can help answer the fundamental questions in plasma physics and improve the understanding of the mechanisms behind astrophysical phenomena, such as formation of collisionless shock waves, deceleration of accretion flows, and evolution of solar (stellar) flares. This work presents the first direct experimental observations of stagnation and redirection of counterstreaming flows (jets) of laser plasma induced by ultra-intense laser pulses with intensity $I \sim$ 2 $\times$ $10^{18}$ $W/cm^2$. Hybrid (PIC - fluid) modeling, which takes into account the kinetic effects of ion motion and the evolution of the pressure tensor for electrons, demonstrates the compression of counterdirected toroidal self-generated magnetic fields embedded in the counterstreaming plasma flows. The enhancement of the toroidal magnetic field in the interaction region results in plasma flow stagnation and redirection of the jets across the line of their initial propagation.

physics.plasm-ph↗
arXiv2020

Status of a point-like neutron generator development

In this paper we report on a high current density ion beam profile diagnostics with a slit-based system as a reliable method, capable of high thermal load applications. The task arose in frames of a point-like neutron source development for neutron radiography. In previous research, it was suggested to construct such a system as a D-D neutron generator based on the high current gasdynamic ion source, which utilises the plasma of electron cyclotron resonance discharge sustained by powerful millimeter wave gyrotron radiation. This device is able to produce focused D+ beams with a characteristic diameter of 1 mm, total current above 100 mA, and current density at a level of several A/cm^2. Study of such intense beams profile to obtain the best focusing efficiency and minimize neutron producing area appeared to be a challenging task. The paper also demonstrates the possibility of fast neutron imaging with a point-like powerful neutron generator (neutron yield on the level of 10^10 1/s).

physics.plasm-ph↗
arXiv2020

Pulsed magnetic field generation system for laser-plasma research

An up to 15 T pulsed magnetic field generator in a volume of a few cubic centimeters has been created for experiments with magnetized laser plasma. The magnetic field is created by a pair of coils placed in a sealed reservoir with liquid nitrogen, which is installed in a vacuum chamber with a laser target. The bearing body provides the mechanical strength of the system both in the case of co-directional and oppositely connected coils. The configuration of the housing allows laser radiation to be introduced into the working area between the coils in a wide range of directions and focusing angles, to place targets away from the symmetry axis of the magnetic system, and to irradiate several targets simultaneously.

physics.app-ph↗
arXiv2019

Structural features of sun photosphere under high spatial resolution

The main small-scale elements observed in the solar photosphere at high resolution are discussed: granules, faculaes, micropores. As a separate element of the fine structure, a continuous network of dark intergranular gaps is considered. The results of image processing of micropores and faculaes knots obtained using modern adaptive telescopes are presented. For intergranular gaps and micropores, a stationary regime of magnetic diffusion is determined, in which horizontal-vertical plasma flows converging to the gap (and micropores) compensate for the dissipative spreading of the magnetic flux on a given scale. A theoretical assessment of the characteristic scales of these structures in the photosphere is obtained: 20-30 km for the thickness of dark intergranular spaces and 200-400 km for the diameter of micropores.

astro-ph.SR↗
arXiv2018

The global oscillations of the sun from tsi, soho and sdo data

The global oscillations of the Sun are investigated on the base of three independent sets of data: 1. Records of Total Solar Irradiance (TSI). 2. The average brightness of the photosphere in MDI (SOHO) and HMI (SDO) images. 3. Records of the time variations of sunlight reflected from the planets during their passage in the field of view of the LASCO C3 coronagraph. It is found that in the low-frequency spectrum of solar oscillations as a star there are modes of 8-10, 36-38 hours and the main stable 9-day mode. The last mode can be regarded as a reflection of oscillatory processes near the fast rotating core of the Sun according to Fossat et al. (2017).

astro-ph.SR↗
arXiv2018

Long-Term Oscillations of Sunspots and a Special Class of Artifacts in SOHO(MDI) and SDO(HMI) Data

A specific type of artifacts, that originate due to displacement of the image of a moving object along the digital (pixel) matrix of receiver are analyzed in detail. The criteria of appearance and the influence of these artifacts on the study of long-term oscillations of sunspots are deduced. The obtained criteria suggest us methods for reduction or even elimination of these artifacts. It is shown that the use of integral parameters can be very effective against the artifact distortions. The simultaneous observations of sunspot magnetic field and ultraviolet intensity of the umbra have given the same periods for the long-term oscillations. In this way the real physical nature of the oscillatory process, which is independent of the artifacts have been confirmed again. A number of examples considered here confirm the dependence between the periods of main mode of the sunspot magnetic field long-term oscillations and its strength. The dependence was derived earlier from both the observations and the theoretical model of the shallow sunspot. The anti-phase behavior of time variations of sunspot umbra area and magnetic field of the sunspot demonstrates that the umbra of sunspot moves in long-term oscillations as a whole: all its points oscillate with the same phase.

astro-ph.SR↗
arXiv2016

Ultra Low-Frequency Oscillations of a Solar Filament in Hα Revealed With the Data of the Global Oscillation Network Group (Gong)

The data of ground-based telescopes of Global Oscillation Network Group (GONG) obtained in the H-alpha line provide an opportunity to study the long-period oscillations of chromospheric filaments (quiescent prominence). For the first time, on the base of time-series of 5 days duration, combined from the observations of three observatories of the GONG, a new ultra-low mode, with period between 20 and 30 hours, was reliably detected in oscillations of a long-lived dark filament on the solar disc.

astro-ph.SR↗
arXiv2011

Statistical estimation of the quality of quantum-tomography protocols

We present a complete methodology for testing the performances of quantum tomography protocols. The theory is validated by several numerical examples and by the comparison with experimental results achieved with various protocols for whole families of polarization states of qubits and ququaters including pure, mixed, entangled and separable.

quant-ph↗