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Search Results: 1 - 10 of 248009 matches for " G. Yu. Lyubarsky "
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The First Eocene Species of the Genus Cryptophagus (Coleoptera, Clavicornia, Cryptophagidae)
G. Yu. Lyubarsky, E. E. Perkovsky
Vestnik Zoologii , 2012, DOI: 10.2478/v10058-012-0007-z
Abstract: Based on a fossil specimen from the Late Eocene Rovno amber (Ukraine), Cryptophagus harenus Lyubarsky et Perkovsky, sp. n., an Eocene species of this genus is described. The new species is similar to the extant desert species Cryptophagus desertus Lyubarsky and C. recticollis Solsky, differing by the large callosity occupying 1/4 length of lateral margin of pronotum.
About chaotization mechanisms of the distributed dynamical systems which are close to discrete
Yu. P. Bliokh,M. G. Lyubarsky,V. O. Podobinsky
Discrete Dynamics in Nature and Society , 1996, DOI: 10.1155/s102602269700023x
Abstract: The investigations of stochastization mechanisms of distributed dynamical systems (DDS) are developed not so complete as stochastization of dynamical systems with concentrated parameters (CDS). Therefore the corresponding DDS which is close (in one or other sense) to the CDS under consideration is used. Such substitution means some roughening of an initial problem. However, there are such important stochastization mechanisms understanding properties, which are connected with system ¢ € distributivity ¢ € on principle. In this paper the conception of a proximity to the CDS is introduced for one particular class of the DDS. It is shown that such kind of systems has two stochastization mechanisms, one of which is common to the DDS and the corresponding CDS. Another stochastization mechanism inherent in DDS disappears under transition from DDS to CDS.
Reconnection in a striped pulsar wind
Y. Lyubarsky,J. G. Kirk
Physics , 2000, DOI: 10.1086/318354
Abstract: It is generally thought that most of the spin-down power of a pulsar is carried away in an MHD wind dominated by Poynting flux. In the case of an oblique rotator, a significant part of this energy can be considered to be in a low-frequency wave, consisting of stripes of toroidal magnetic field of alternating polarity, propagating in a region around the equatorial plane. Magnetic reconnection in such a structure has been proposed as a mechanism for transforming the Poynting flux into particle energy in the pulsar wind. We have re-examined this process and conclude that the wind accelerates significantly in the course of reconnection. This dilates the timescale over which the reconnection process operates, so that the wind requires a much larger distance than was previously thought in order to convert the Poynting flux to particle flux. In the case of the Crab, the wind is still Poynting-dominated at the radius at which a standing shock is inferred from observation. An estimate of the radius of the termination shock for other pulsars implies that all except the milli-second pulsars have Poynting-flux dominated winds all the way out to the shock front.
Reconnection in pulsar winds
J. G. Kirk,Y. Lyubarsky
Physics , 2001, DOI: 10.1071/AS01046
Abstract: The spin-down power of a pulsar is thought to be carried away in an MHD wind in which, at least close to the star, the energy transport is dominated by Poynting flux. The pulsar drives a low-frequency wave in this wind, consisting of stripes of toroidal magnetic field of alternating polarity, propagating in a region around the equatorial plane. The current implied by this configuration falls off more slowly with radius than the number of charged particles available to carry it, so that the MHD picture must, at some point, fail. Recently, magnetic reconnection in such a structure has been shown to accelerate the wind significantly. This reduces the magnetic field in the comoving frame and, consequently, the required current, enabling the solution to extend to much larger radius. This scenario is discussed and, for the Crab Nebula, the range of validity of the MHD solution is compared with the radius at which the flow appears to terminate. For sufficiently high particle densities, it is shown that a low frequency entropy wave can propagate out to the termination point. In this case, the "termination shock" itself must be responsible for dissipating the wave.
Asymptotic structure of Poynting dominated jets
Yuri Lyubarsky
Physics , 2009, DOI: 10.1088/0004-637X/698/2/1570
Abstract: In relativistic, Poynting dominated outflows, acceleration and collimation are intimately connected. An important point is that the Lorentz force is nearly compensated by the electric force therefore the acceleration zone spans a large range of scales. We derived the asymptotic equations describing relativistic, axisymmetric MHD flows far beyond the light cylinder. These equations do not contain either intrinsic small scales (like the light cylinder radius) or terms that nearly cancel each other (like the electric and magnetic forces) therefore they could be easily solved numerically. They also suit well for qualitative analysis of the flow and in many cases, they could even be solved analytically or semi-analytically. We show that there are generally two collimation regimes. In the first regime, the residual of the hoop stress and the electric force is counterbalanced by the pressure of the poloidal magnetic field so that at any distance from the source, the structure of the flow is the same as the structure of an appropriate cylindrical equilibrium configuration. In the second regime, the pressure of the poloidal magnetic field is negligible small so that the flow could be conceived as composed from coaxial shrinking magnetic loops. In the two collimation regimes, the flow is accelerated in different ways. We study in detail the structure of jets confined by the external pressure with a power law profile. In particular, we obtained simple scalings for the extent of the acceleration zone, for the terminal Lorentz factor and for the collimation angle.
Adjustment of the electric charge and current in pulsar magnetospheres
Yuri Lyubarsky
Physics , 2009, DOI: 10.1088/0004-637X/696/1/320
Abstract: We present a simple numerical model of the plasma flow within the open field line tube in the pulsar magnetosphere. We study how the plasma screens the rotationally induced electric field and maintains the electric current demanded by the global structure of the magnetosphere. We show that even though bulk of the plasma moves outwards with relativistic velocities, a small fraction of particles is continuously redirected back forming reverse plasma flows. The density and composition (positrons or electrons, or both) of these reverse flows are determined by the distribution of the Goldreich-Julian charge density along the tube and by the global magnetospheric current. These reverse flows could significantly affect the process of the pair plasma production in the polar cap accelerator. Our simulations also show that formation of the reverse flows is accompanied by the generation of long wavelength plasma oscillations, which could be converted, via the induced scattering on the bulk plasma flow, into the observed radio emission.
A model for fast extragalactic radio bursts
Yuri Lyubarsky
Physics , 2014, DOI: 10.1093/mnrasl/slu046
Abstract: Bursts of millisecond duration were recently discovered in the 1 GHz band. There is a strong evidence that they come from $\sim 1 $ Gpc distances, which implies extraordinary high brightness temperature. I propose that these bursts could be attributed to synchrotron maser emission from relativistic, magnetized shocks. At the onset of the magnetar flare, a strongly magnetized pulse is formed, which propagates away through the relativistic magnetar wind and eventually reaches the nebula inflated by the wind within the surrounding medium. I show that the observed radio bursts could be generated at shocks formed via the interaction of the magnetic pulse with the plasma within the nebula. The model predicts strong millisecond bursts in the TeV band, which could be observed even from distant galaxies.
Adjustment of the electric current in pulsar magnetospheres and origin of subpulse modulation
Yuri Lyubarsky
Physics , 2012, DOI: 10.1007/s10509-012-1143-1
Abstract: The subpulse modulation of pulsar radio emission goes to prove that the plasma flow in the open field line tube breaks into isolated narrow streams. I propose a model which attributes formation of streams to the process of the electric current adjustment in the magnetosphere. A mismatch between the magnetospheric current distribution and the current injected by the polar cap accelerator gives rise to reverse plasma flows in the magnetosphere. The reverse flow shields the electric field in the polar gap and thus shuts up the plasma production process. I assume that a circulating system of streams is formed such that the upward streams are produced in narrow gaps separated by downward streams. The electric drift is small in this model because the potential drop in narrow gaps is small. The gaps have to drift because by the time a downward stream reaches the star surface and shields the electric field, the corresponding gap has to shift. The transverse size of the streams is determined by the condition that the potential drop in the gaps is sufficient for the pair production. This yields the radius of the stream roughly 10% of the polar cap radius, which makes it possible to fit in the observed morphological features such as the "carousel" with 10-20 subbeams and the system of the core - two nested cone beams.
Asymptotic theory of relativistic, magnetized jets
Yuri Lyubarsky
Physics , 2010, DOI: 10.1103/PhysRevE.83.016302
Abstract: The structure of a relativistically hot, strongly magnetized jet is investigated at large distances from the source. Asymptotic equations are derived describing collimation and acceleration of the externally confined jet. Conditions are found for the transformation of the thermal energy into the fluid kinetic energy or into the Poynting flux. Simple scalings are presented for the jet collimation angle and Lorentz factors.
A new mechanism for dissipation of alternating fields in Poynting dominated outflows
Yuri Lyubarsky
Physics , 2010, DOI: 10.1088/2041-8205/725/2/L234
Abstract: Reconnection of alternating magnetic fields is an important energy transformation mechanism in Poynting dominated outflows. We show that the reconnection is facilitated by the Kruskal-Schwarzschild instability of current sheets separating the oppositely directed fields. This instability, which is a magnetic counterpart of the Rayleigh-Taylor instability, develops if the flow is accelerated. Then the plasma drips out of the current sheet providing conditions for rapid reconnection. Since the magnetic dissipation leads to the flow acceleration, the process is self-sustaining. In pulsar winds, this process could barely compete with the earlier proposed dissipation mechanisms. However, the novel mechanism turns out to be very efficient at AGN and GRB conditions.
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