arXiv subjects

Z. Osmanov

Publications and source records attributed to Z. Osmanov.

At least 19 recordsLinked to original sources

arXiv2021

A novel mechanism of pair creation in pulsar magnetospheres

In this paper we study the possibility of efficient pair production in a pulsar's magnetosphere. It has been shown that by means of the relativistic centrifugal force the electrostatic field exponentially amplifies. As a result the field approaches the Schwinger limit leading to pair creation process in the light cylinder area where the effects of rotation are very efficient. Analysing the parameters of the normal period ($\sim 1$ sec) pulsars we have found that the process is so efficient that the number density of electron-positron pairs exceeds the Goldreich-Julian density by five orders of magnitude.

astro-ph.HE↗

arXiv2020

Electromagnetic Vortex solitons in the magnetospheres of super-Eddington AGN

Propagation and dynamics of electromagnetic vortex solitons have been studied in the electron positron ion plasmas of super-Eddington active galactic nuclei (AGN). Existence and stability of such structures is demonstrated for highly transparent AGN plasma media. Possible implications of dynamical features and corresponding observational signatures are discussed.

astro-ph.HE↗

arXiv2020

On a spectral pattern of the Von-Neumann probes

In this paper we have extended our previous work \citep{probe1} and considered spectral characteristics of interstellar non-relativistic Type-II and Type-III Von-Neumann probes. It has been shown that by means of the proton capture, required for replication, strong bremstrahlung emission will be generated. We have found that for both types of civilizations the probes might be visible mainly in the infrared spectral band, but as it has been found the probes might be visible in the ultraviolet as well. For both cases it was shown that differential power has dips for equally spaced frequencies, which might be a significant fingerprint to identify such exotic interstellar objects.

physics.pop-ph↗

arXiv2020

Synchrotron emission from the depths of pulsar magnetospheres

In this paper we study the generation of high energy emission from normal pulsars. For this purpose we consider the particles accelerated in the outer magnetosphere sliding along the closed magnetic field lines. It has been shown that in due course of motion the initial small pitch angle increases and at a certain distance from the neutron star the synchrotron emission becomes significant. We found that a region covered from $150$ to $500$ stellar radii the emission pattern is characterised by energies in the interval $(0.1-10)$ MeV.

astro-ph.HE↗

arXiv2019

On the shear flow instability in the great red spot of Jupiter

In the present paper we study instability caused by the velocity shear flows of the great red spot of Jupiter. For the purpose, we imply the Navier Stokes and the continuity equations, perform the linear analysis of the governing equations and numerically solve them. We have considered two different regimes: exponential and harmonic behaviour of wave vectors. It has been shown that both scenarios reveal unstable character of flows and the corresponding rate might be considerably high. For the case of harmonic time dependence of wave vectors we also found a beat like solution of sound waves.

astro-ph.EP↗

arXiv2019

Anomalous Variability of Dyson Megastructures

In the framework of the approach of Dyson megastructures, by assuming that a super-advanced civilization exists and is capable of constructing a ring-like megastructure around their host star, we have considered the observational signatures of cold (300 K) and hot (4000) K astro-engineering to answer the question: are the modern facilities capable to detect theoretically predicted fingerprints? By implying the spectral resolving power and the radial velocity methods it has been shown that the oscillation of the rings might be detected as anomalous variability of the megastructures.

physics.pop-ph↗

arXiv2019

On the interstellar Von Neumann micro self-reproducing probes

In this paper we consider efficiency of self-reproducing extraterrestrial Von-Neumann micro scale robots and analyse the observational characteristics. By examining the natural scenario of moving in the HII clouds, it has been found that the timescale of replication might be several years and even less - making the process of observation quite promising. We have shown that by encountering the interstellar protons the probes might be visible at least in the infrared energy band and the corresponding luminosities might reach enormous values.

physics.pop-ph↗

arXiv2019

Rotationally-driven VHE emission from the Vela pulsar

The recent detection of pulsed $γ$-ray emission from the Vela pulsar in the $\sim10$ to 100 GeV range by H.E.S.S. promises an important potential to probe into the very high energy (VHE) radiation mechanisms of pulsars. The recent detection of pulsed $γ$-ray emission from the Vela pulsar in the $\sim10$ to 100 GeV range by H.E.S.S. promises an important potential to probe into the very high energy (VHE) radiation mechanisms of pulsars. We analyze achievable particle energies in the magnetosphere of the Vela pulsar, and calculate the resultant emission properties. Inverse Compton up-scattering of thermal photons from the surface of the star is shown to lead a pulsed VHE contribution reaching into the TeV regime with spectral characteristics compatible with current findings. If confirmed by further observations this could be the second case where rotationally-driven processes turn out to be important to understand the VHE emission in young pulsars.

astro-ph.HE↗

arXiv2018

On the Filamentation Instability in Degenerate Relativistic Plasmas

The filamentation instability of the electromagnetic (EM) beam in an underdense plasma with high level of degeneracy is examined by means of the momentum equation, continuity equation and Maxwell's equations. It has been demonstrated that the instability develops for weakly as well as strongly relativistic degenerate plasma and arbitrary strong amplitude of EM beams.

physics.plasm-ph↗

arXiv2018

3D study of centrifugal acceleration in isotropic photon fields

In this paper we study relativistic dynamics of charged particles co-rotating with prescribed trajectories, having the shape of dipolar magnetic field lines. In particular, we consider the role of the drag force caused by the photon field the forming of equilibrium positions of the charged particles. Alongside a single particle approach we also study behaviour of ensemble of particles in the context of stable positions. As we have shown, together they create surfaces where particles are at stable equilibrium positions. In this paper we examine these shapes and study parameters they depend on. It has been found that under certain conditions there are two distinct surfaces with stable equilibrium positions.

astro-ph.HE↗

arXiv2018

On the possibility of the Dyson spheres observable beyond the infrared spectrum

In this paper we revisit the Dysonian approach and assume that a superadvanced civilisation is capable of building a cosmic megastructure located closer than the habitable zone (HZ). Then such a Dyson Sphere (DS) might be visible in the optical spectrum. We have shown that for typical high melting point meta material - Graphene, the radius of the DS should be of the order of $10^{11}$cm, or even less. It has been estimated that energy required to maintain the cooling system inside the DS is much less than the luminosity of a star. By considering the stability problem, we have found that the radiation pressure might stabilise dynamics of the megastructure and as a result it will oscillate, leading to interesting observational features - anomalous variability. The similar variability will occur by means of the transverse waves propagating along the surface of the cosmic megastructure. In the summary we also discuss the possible generalisation of definition of HZs that might lead to very interesting observational features.

physics.pop-ph↗

arXiv2018

The role of second viscosity in the velocity shear-induced heating mechanism

In the present paper we study the influence of second viscosity on non-modally induced heating mechanism. For this purpose we study the set of equations governing the hydrodynamic system. In particular, we consider the Navier Stokes equation, the continuity equation and the equation of state, linearise them and analyse in the context of non-modal instabilities. Unlike previous studies in the Navier Stokes equation we include the contribution of compressibility, thus the second viscosity. By analysing several typical cases we show that under certain conditions the second viscosity might significantly change efficiency of the mechanism of heating.

physics.plasm-ph↗

arXiv2018

Efficiency of Centrifugal Mechanism in Producing PeV Neutrinos From Active Galactic Nuclei

A several-step theoretical model is constructed to trace the origin of ultra high energy (UHE) $[1-2]$PeV neutrinos detected, recently, by the IceCube collaboration. Protons in the AGN magnetosphere, experiencing different gravitational centrifugal force, provide free energy for the parametric excitation of Langmuir waves via a generalized two-stream instability. Landau damping of these waves, outside the AGN magnetosphere, can accelerate protons to ultra high energies. The ultimate source for this mechanism, the Langmuir-Landau-Centrifugal-Drive (LLCD), is the gravitational energy of the compact object. The LLCD generated UHE protons provide the essential ingredient in the creation of UHE neutrinos via appropriate hadronic reactions; protons of energy~ $10^{17}$eV can be generated in the plasmas surrounding AGN with bolometric luminosities of the order of $10^{43}$ergs s$^{-1}$. By estimating the diffusive energy flux of extragalactic neutrinos in the energy interval $[1-2]$PeV, we find that an acceptably small fraction $0.003\%$ of the total bolometric luminosity will suffice to create the observed fluxes of extragalactic ultra-high energy neutrinos.

astro-ph.HE↗

arXiv2017

Centrifugal acceleration in the isotropic photon field

In this paper we study centrifugal acceleration of particles moving along a prescribed rotating curved trajectories. We consider the physical system embedded in an isotropic photon field and study the influence of the photon drag force on the acceleration process. For this purpose we study three major configurations of the field lines: the straight line; the Archimede's spiral and the dipolar field line configuration. By analysing dynamics of particles sliding along the field lines in the equatorial plane we have found several interesting features of motion. In particular, it has been shown that for rectilinear field lines the particles reach the light cylinder (area where the linear velocity of rotation exactly equals the speed of light) zone relatively slowly for bigger drag forces. Considering the Archimede's spiral, we have found that in cases when the field lines lag behind the rotation, the particles achieve the force-free regime of dynamics regardless of the drag force. Unlike this scenario, when the spiral is screwed up in an opposite direction there the particles do not reach the force free regime, but tend to stable equilibrium locations. Such a behaviour has been found for straight field lines as well.

astro-ph.HE↗

arXiv2017

Particles on the rotating channels in the wormhole metrics

In the Ellis-Bronnikov wormhole (WH) metrics the motion of a particle along curved rotating channels is studied. By taking into account a prescribed shape of a trajectory we derive the reduced $1+1$ metrics, obtain the corresponding Langrangian of a free particle and analytically and numerically solve the corresponding equations of motion. We have shown that if the channels are twisted and lag behind rotation, under certain conditions beads might asymptotically reach infinity, leaving the WH, which is not possible for straight co-rotating trajectories. The analytical and numerical study is performed for two and three dimensional cases and initial conditions of particles are analysed in the context of possibility of passing through the WH.

astro-ph.HE↗

arXiv2017

Are the Dyson rings around pulsars detectable?

In the previous paper (Osmanov 2016) (henceforth Paper-I) we have extended the idea of Freeman Dyson and have shown that a supercivilization has to use ring-like megastructures around pulsars instead of a spherical shell. In this work we reexamine the same problem in the observational context and we show that facilities of modern IR telescopes (VLTI and WISE) might efficiently monitor the nearby zone of the solar system and search for the IR Dyson-rings up to distances of the order of $0.2$kpc, corresponding to the current highest achievable angular resolution, $0.001$mas. In this case the total number of pulsars in the observationally reachable area is about $64\pm 21$. We show that pulsars from the distance of the order of $\sim 1$kpc are still visible for WISE as point-like sources but in order to confirm that the object is the neutron star, one has to use the UV telescopes, which at this moment cannot provide enough sensitivity.

astro-ph.HE↗

arXiv2017

Development of non-modal shear induced instabilities in atmospheric tornadoes

In this paper we consider the role of nonmodal instabilities in the dynamics of atmospheric tornadoes. For this purpose we consider the Euler equation, continuity equation and the equation of state and linearise them. As an example we study several different velocity profiles: the so-called Rankine vortex model; the Burgers-Rott vortex model; Sullivan and modified Sullivan vortex models. It has been shown that in the two dimensional Rankine vortex model no instability appears in the inner region of a tornado. On the contrary, outside this area the physical system undergoes strong exponential instability. We have found that initially perturbed velocity components lead to amplified sound wave excitations. The similar results have been shown in Burgers-Rott vortex model as well. As it was numerically estimated, in this case, the unstable wave increases its energy by a factor of $400$ only in $\sim 0.5$min. According to the numerical study, in Sullivan and modified Sullivan models, the instability does not differ much by the growth. Despite the fact that in the inner area the exponential instability does not appear in a purely two dimensional case, we have found that in the modified Sullivan vortex even a small contribution from vertical velocities can drive unstable nonmodal waves.

physics.ao-ph↗

arXiv2016

On the rotationally driven pevatron in the centre of the Milky Way

Based on the collective linear and nonlinear processes in a magnetized plasma surrounding the black hole at the galactic center (GC), an acceleration mechanism is proposed to explain the recent detection/discovery of PeV protons. In a two stage process, the gravitation energy is first converted to the electrical energy in fast growing Langmuir waves, and then the electrical energy is transformed to the particle kinetic energy through Landau damping of waves. It is shown that, for the characteristics parameters of GC plasma, proton energy can be boosted upto 5PeV.

astro-ph.HE↗