arXiv subjects

Zaza Osmanov

Publications and source records attributed to Zaza Osmanov.

At least 19 recordsLinked to original sources

arXiv2021

The effect of motion of respiratory droplets on propagation of viral particles

In this work we investigate viral load propagation due to liquid droplets expelled during respiratory actions. We describe a mechanism of the transmission of such evaporating system and analyze dependence on several ambient parameters for different respiratory processes, such as sneezing, coughing and speaking. Our study has found that a significant amount of viral load and droplets from the respiratory fluid might transfer beyond the customary 2m distance, understanding of which might give us a better insight about regulations and risks posed by an infected individual.

physics.med-ph↗

arXiv2021

Can China's FAST telescope detect extraterrestrial von-Neumann probes?

In the present paper we consider the Type-2.x and Type-3.x extraterrestrial von-Neumann probes and study the problem of their detectability by the world's largest radio telescope: the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). For this purpose we estimate the radio spectral parameters and analyse the obtained results in the context of technical characteristics of FAST. As a result, it is shown that FAST can detect as galactic as well as extragalactic self-replicating probes with high precision.

physics.pop-ph↗

arXiv2021

On the resolution of a weak Fermi paradox

In this paper we consider the Fermi's paradox (FP) and propose a possible resolution in the context of super-advanced alien civilizations. In this sense it can be regarded as to be the weak Fermi paradox (WFP). By assuming that superadvanced extraterrestrials (ET) exist and are capable of constructing a huge ring-like megastructure around a pulsar or a main sequence star (MSS) to consume its emitted energy, we consider the stability problem of the ring, studying the out of plane dynamics. It has been shown that for normal pulsars the oscillation timescale, thus the timescale of the spectral variability is of the order of several days, whereas for MSS it can vary from minutes up to hundreds of years. We have shown that by means of the high resolving power and sensitivity, the European Southern Observatory's Very Large Telescope can detect either cold ($T=300$ K) or hot ($T=4000$ K) megastructures throughout the whole galaxy even for very small oscillation amplitudes of rings. As it is shown the observed variability can have characteristics similar to those of some other variables, which can be considered as one of the resolutions of the WFP.

physics.pop-ph↗

arXiv2021

On the heating of AGN magnetospheres

The Langmuir-Landau-Centrifugal Drive (LLCD), that can effectively "convert" gravitational energy into particles, is explored as a driving mechanism responsible for the extreme thermal luminosity acquired by some active galactic nuclei (AGN). For this purpose we consider equations governing the process of heating of AGN magnetospheres. In particular, we examine the Fourier components of the momentum equation, the continuity equation and the Poisson equation in the linear approximation and estimate the growth rate of the centrifugally excited electrostatic waves and the increment of the Langmuir collapse. It is shown that the process of energy pumping is composed of three stages: in the first stage the energy is efficiently transferred from rotation to the electrostatic modes. In due course of time, the second regime - the Langmuir collapse - occurs, when energy pumping is even more efficient. This process is terminated by the Landau damping, when enormous energy is released in the form of heat. We show that the magnetospheres of the supermassive black holes with luminosities of the order of $10^{45-46}$erg/s can be heated up to $10^{6-10}$K.

astro-ph.GA↗

arXiv2021

From the SpaceX Starlink megaconstellation to the search for Type-I civilizations

Here we extrapolate the idea of launching SpaceX's Starlink satellites and study the possibility of building planetary megastructures (either designed as solid objects or as a web of satellites) by Type-I civilizations and the consequent detection of their techno-signatures. We have shown that the instruments of The Very Large Telescope Interferometer (VLTI) can potentially observe emission pattern of the huge constructions. Efficiency of the spectral variability method has been emphasized and the role of the FAST telescope was discussed.

physics.pop-ph↗

arXiv2015

On the role of rotation in the outflows of the Crab pulsar

In order to study constraints imposed on kinematics of the Crab pulsar's jet we consider motion of particles along co-rotating field lines in the magnetosphere of the Crab pulsar. It is shown that particles following the co-rotating magnetic field lines may attain velocities close to observable values. In particular, we demonstrate that if the magnetic field lines are within the light cylinder, the maximum value of the velocity component parallel to the rotation axis is limited by $0.5c$. This result in the context of the $X$-ray observations performed by {\it Chandra X-ray Observatory} seems to be quite indicative and useful to estimate the density of field lines inside the jet. Considering the three-dimensional (3D) field lines crossing the light cylinder, we found that for explaining the force-free regime of outflows the magnetic field lines must asymptotically tend to the Archimedes' spiral configuration. It is also shown that the 3D case may explain the observed jet velocity for appropriately chosen parameters of magnetic field lines.

astro-ph.SR↗

arXiv2014

Extremely efficient Zevatron in rotating AGN magnetospheres

A novel model of particle acceleration in the magnetospheres of rotating active galactic nuclei (AGN) is constructed.The particle energies may be boosted up to $10^{21}$eV in a two step mechanism: In the first stage, the Langmuir waves are centrifugally excited and amplified by means of a parametric process that efficiently pumps rotational energy to excite electrostatic fields. In the second stage, the electrostatic energy is transferred to particle kinetic energy via Landau damping made possible by rapid "Langmuir collapse". The time-scale for parametric pumping of Langmuir waves turns out to be small compared to the kinematic time-scale, indicating high efficiency of the first process. The second process of "Langmuir collapse" - the creation of caverns or low density regions - also happens rapidly for the characteristic parameters of the AGN magnetosphere. The Langmuir collapse creates appropriate conditions for transferring electric energy to boost up already high particle energies to much higher values. It is further shown that various energy loss mechanism are relatively weak, and do not impose any significant constraints on maximum achievable energies.

astro-ph.HE↗

arXiv2014

Radio emission of magnetars driven by the quasi-linear diffusion

In this, paper we study the possibility of generation of electromagnetic waves in the magnetospheres of radio magnetars by means of the quasi-linear diffusion (QLD). Considering the magnetosphere composed of the so-called beam and the plasma components respectively, we argue that the frozen-in condition will inevitably lead to the generation of the unstable cyclotron modes. These modes, via the QLD, will in turn influence the particle distribution function, leading to certain values of the pitch angles, thus to an efficient synchrotron mechanism, producing radio photons. We show that for three known radio magnetars the QLD might be a realistic mechanism for producing photons in the radio band.

astro-ph.SR↗

arXiv2013

Ultra High Energy Electrons Powered by Pulsar Rotation

A new mechanism of particle acceleration to ultra high energies, driven by the rotational slow down of a pulsar (Crab pulsar, for example), is explored. The rotation, through the time dependent centrifugal force, can very efficiently excite unstable Langmuir waves in the e-p plasma of the star magnetosphere via a parametric process. These waves, then, Landau damp on electrons accelerating them in the process. The net transfer of energy is optimal when the wave growth and the Landau damping times are comparable and are both very short compared to the star rotation time. We show, by detailed calculations, that these are precisely the conditions for the parameters of the Crab pulsar. This highly efficient route for energy transfer allows the electrons in the primary beam to be catapulted to multiple TeV ($\sim 100$ TeV) and even PeV energy domain. It is expected that the proposed mechanism may, partially, unravel the puzzle of the origin of ultra high energy cosmic ray electrons.

astro-ph.HE↗

arXiv2012

Synchrotron emission driven by the Cherenkov-drift instability in active galactic nuclei

In the present paper we study generation of the synchrotron emission by means of the feedback of Cherenkov drift waves on the particle distribution via the diffusion process. It is shown that despite the efficient synchrotron losses the excited Cherenkov drift instability leads to the quasi-linear diffusion (QLD), effect of which is balanced by dissipation factors and as a result the pitch angles are prevented from damping, maintaining the corresponding synchrotron emission. The model is analyzed for a wide range of physical parameters and it is shown that the mechanism of QLD guarantees the generation of electromagnetic radiation from soft $X$-rays up to soft $γ$-rays, strongly correlated with Cherenkov drift emission ranging from IR up to UV energy domains.

astro-ph.HE↗

arXiv2012

On the mechanism of the pulsed high energy emission from the pulsar PSR B1509-58

We investigate the high-energy (HE) ($<1$GeV) emission from the pulsar PSR B1509-58 and its relation to the radio emission in the 1.4GHz frequency band. The role of the quasi-linear diffusion in producing the pulsed HE radiation is investigated. We show that by means of the cyclotron instability the relatively low frequency waves excite, which due to the diffusion process influence the particle distribution function and switch on the synchrotron emission mechanism. We argue that the coincidence of HE main peak and the radio pulse is a direct consequence of the fact that the high and low frequency radiation is produced simultaneously in a local area of the pulsar magnetosphere. In the paper we also consider the absence of the radio counter pulse and explain this fact.

astro-ph.HE↗

arXiv2012

Self-heating in kinematically complex magnetohydrodynamic flows

The non-modal self-heating mechanism driven by the velocity shear in kinematically complex magnetohydrodynamic (MHD) plasma flows is considered. The study is based on the full set of MHD equations including dissipative terms. The equations are linearized and unstable modes in the flow are looked for. Two different cases are specified and studied: (a) the instability related to an exponential evolution of the wave vector; and (b) the parametric instability, which takes place when the components of the wave vector evolve in time periodically. By examining the dissipative terms, it is shown that the self-heating rate provided by viscous damping is of the same order of magnitude as that due to the magnetic resistivity. It is found that the heating efficiency of the exponential instability is higher than that of the parametric instability.

astro-ph.SR↗

arXiv2012

On the spectrum of the pulsed gamma-ray emission from 10MeV to 400GeV of the Crab pulsar

In the present paper a self-consistent theory, interpreting the VERITAS observations of the very high energy pulsed emission from the Crab pulsar is considered. The photon spectrum between 10MeV and 400GeV can be described by two power-law functions with the spectral indexes equal to 2 and 3.8. The source of the pulsed emission above 10MeV is assumed to be the synchrotron radiation, which is generated near the light cylinder during the quasi-linear stage of the cyclotron instability. The emitting particles are the primary beam electrons with the Lorentz factors up to $10^{9}$. Such high energies by beam particles is supposed to be reached due to Landau damping of the centrifugally induced Langmuir waves. This mechanism provides simultaneous generation of low (radio) and high energy (10MeV-400GeV) emission on the light cylinder scales, in one location of the pulsar magnetosphere.

astro-ph.HE↗

arXiv2009

Self-heating and its possible relationship to chromospheric heating in slowly rotating stars

The efficiency of nonmodal self-heating by acoustic wave perturbations is examined. Considering different kinds of kinematically complex velocity patterns we show that nonmodal instabilities arising in these inhomogeneous flows may lead to significant amplification of acoustic waves. Subsequently, the presence of viscous dissipation damps these amplified waves and causes the energy transfer back to the background flow in the form of heat; viz. closes the "self-heating" cycle and contributes to the net heating of the flow patterns and the chromospheric network as a whole. The acoustic self-heating depends only on the presence of kinematically complex flows and dissipation. It is argued that together with other mechanisms of nonlinear nature the self-heating \textit{may be} a probable additinal mechanism of nonmagnetic chromospheric heating in the Sun and other solar-type stars with slow rotation and extended convective regions.

astro-ph.SR↗

arXiv2009

On particle acceleration and very high energy gamma-ray emission in Crab-like pulsars

The origin of very energetic charged particles and the production of very high-energy (VHE) gamma-ray emission remains still a challenging issue in modern pulsar physics. By applying a toy model, we explore the acceleration of co-rotating charged particles close to the light surface in a plasma-rich pulsar magnetosphere and study their interactions with magnetic and photon fields under conditions appropriate for Crab-type pulsars. Centrifugal acceleration of particles in a monopol-like magnetic field geometry is analyzed and the efficiency constraints, imposed by corotation, inverse Compton interactions and curvature radiation reaction are determined. We derive expressions for the maximum particle energy and provide estimates for the corresponding high-energy curvature and inverse Compton power outputs. It is shown that for Crab-like pulsars, electron Lorentz factor up to $γ\sim 10^7$ can be achieved, allowing inverse Compton (Klein-Nishina) up-scattering of thermal photons to TeV energies with a maximum luminosity output of $\sim10^{31}$ erg/s. Curvature radiation, on the other hand, will result in a strong GeV emission output of up to $\sim(10^{34}-10^{35})$ erg/s, quasi-exponentially decreasing towards higher energies for photon energies below $\sim 50$ GeV. Accordingly to the results presented only young pulsars are expected to be sites of detectable VHE $γ$-ray emission.

astro-ph.HE↗

arXiv2007

On the efficiency of particle acceleration by rotating magnetospheres in AGN

To investigate the efficiency of centrifugal acceleration of particles as a possible mechanism for the generation of ultra-high $γ$-ray nonthermal emission from TeV blazars, we study the centrifugal acceleration of electrons by rotating magnetic field lines, for an extended range of inclination angles and determine the maximum Lorentz factors $γ_{max}$ attainable by the electrons via this process. {Two principal limiting mechanisms for the particle acceleration, inverse Compton scattering and breakdown of the bead-on-the-wire approximation, are examined. Particles may be centrifugally accelerated up to $γ_{max} \simeq 10^8$ and the main limiting mechanism for the $γ_{max}$ is the inverse Compton scattering. The energy of centrifugally accelerated particles can be amply sufficient for the generation (via inverse Compton scattering) of the ultra-high energy (up to $20TeV$) gamma emission in TeV blazars.

astro-ph↗

arXiv2006

Parametric mechanism of the rotation energy pumping by a relativistic plasma

An investigation of the kinematics of a plasma stream rotating in the pulsar magnetosphere is presented. On the basis of an exact set of equations describing the behavior of the plasma stream, the increment of the instability is obtained, and the possible relevance of this approach for the understanding of the pulsar rotation energy pumping mechanism is discussed.

astro-ph↗

arXiv2003

Centrifugally driven relativistic dynamics on curved trajectories

Motion of test particles along rotating curved trajectories is considered. The problem is studied both in the laboratory and the rotating frames of reference. It is assumed that the system rotates with the constant angular velocity $ω= const$. The solutions are found and analyzed for the case when the form of the trajectory is given by an Archimedes spiral. It is found that particles can reach infinity while they move along these trajectories and the physical interpretation of their behaviour is given. The analogy of this idealized study with the motion of particles along the curved rotating magnetic field lines in the pulsar magnetosphere is pointed out. We discuss further physical development (the conserved total energy case, when $ω\ne const$) and astrophysical applications (the acceleration of particles in active galactic nuclei) of this theory.

astro-ph↗