Particle Acceleration in Pair-Starved Pulsars

We investigate the physical situation above the pulsar polar cap (PC) where the accelerating primaries (electrons) are not capable of producing sufficient numbers of electron-positron pairs at low altitudes (within 1-2 stellar radii above the PC surface) to screen the accelerating electric field, and continue accelerating up to, at least, very high altitudes nearly approaching the light cylinder. We derive an analytic solution for the parallel electric field valid at high altitudes. The solution is based on the physical condition of asymptotic vanishing of the rotationally induced transverse electric field within the magnetic flux tube. This condition constrains the asymptotic value of the effective space charge that determines the distribution of the parallel electric field within the magnetic tube. Our estimates of low- to high-altitude values of the parallel electric field imply the occurrence of a regime of primary acceleration (with the characteristic Lorentz factor up to 1-2 X 10^7) all the way from the PC to the light cylinder limited by curvature-radiation reaction. In this model the primary outflow becomes asymptotically force-free, and may turn into a relativistic wind beyond the light cylinder. Such a solution will apply to both older pulsars producing only inverse Compton scattering pairs and younger very high B pulsars (magnetars). We suggest that pulsars, which are lying below the pair death line, may be radio-quiet gamma-ray sources.Comment: 20 pages, accepted for publication in Ap

Effects of Rotation and Relativistic Charge Flow on Pulsar Magnetospheric Structure

We propose an analytical 3-D model of the open field-line region of a neutron star (NS) magnetosphere. We construct an explicit analytic solution for arbitrary obliquity (angle between the rotation and magnetic axes) incorporating the effects of magnetospheric rotation, relativistic flow of charges (e.g. primary electron beam) along the open field lines, and E X B drift of these charges. Our solution employs the space-charge-limited longitudinal current calculated in the electrodynamic model of Muslimov & Tsygan (1992) and is valid up to very high altitudes nearly approaching the light cylinder. We assume that in the innermost magnetosphere, the NS magnetic field can be well represented by a static magnetic dipole configuration. At high altitudes the open magnetic field lines significantly deviate from those of a static dipole and tend to focus into a cylindrical bundle, swept back in the direction opposite to the rotation, and also bent towards the rotational equator. We briefly discuss some implications of our study to spin-powered pulsars.Comment: 24 pages, 3 figures, accepted for publication in Ap

Pulsar Polar Cap Heating and Surface Thermal X-Ray Emission II. Inverse Compton Radiation Pair Fronts

We investigate the production of electron-positron pairs by inverse Compton scattered (ICS) photons above a pulsar polar cap (PC) and surface heating by returning positrons. This paper is a continuation of our self-consistent treatment of acceleration, pair dynamics and electric field screening above pulsar PCs. We calculate the altitude of the inverse Compton pair formation fronts, the flux of returning positrons and present the heating efficiencies and X-ray luminosities. We revise pulsar death lines implying cessation of pair formation, and present them in surface magnetic field-period space. We find that virtually all known radio pulsars are capable of producing pairs by resonant and non-resonant ICS photons radiated by particles accelerated above the PC in a pure star-centered dipole field, so that our ICS pair death line coincides with empirical radio pulsar death. Our calculations show that ICS pairs are able to screen the accelerating electric field only for high neutron star surface temperatures and magnetic fields. We argue that such screening at ICS pair fronts occurs locally, slowing but not turning off acceleration of particles until screening can occur at a curvature radiation (CR) pair front at higher altitude. In the case where no screening occurs above the PC surface, we anticipate that the pulsar gamma-ray luminosity will be a substantial fraction of its spin-down luminosity. The X-ray luminosity resulting from PC heating by ICS pair fronts is significantly lower than the PC heating luminosity from CR pair fronts, which dominates for most pulsars. PC heating from ICS pair fronts is highest in millisecond pulsars, which cannot produce CR pairs, and may account for observed thermal X-ray components in the spectra of these old pulsars.Comment: 29 pages, 10 figures, accepted for publication in Ap

Direct simulations of helical Hall-MHD turbulence and dynamo action

Direct numerical simulations of turbulent Hall dynamos are presented. The evolution of an initially weak and small scale magnetic field in a system maintained in a stationary turbulent regime by a stirring force at a macroscopic scale is studied to explore the conditions for exponential growth of the magnetic energy. Scaling of the dynamo efficiency with the Reynolds numbers is studied, and the resulting total energy spectra are found to be compatible with a Kolmogorov type law. A faster growth of large scale magnetic fields is observed at intermediate intensities of the Hall effect.Comment: 13 pages, 17 figures, ApJ (in press

Force-free magnetosphere of an aligned rotator with differential rotation of open magnetic field lines

Here we briefly report on results of self-consistent numerical modeling of a differentially rotating force-free magnetosphere of an aligned rotator. We show that differential rotation of the open field line zone is significant for adjusting of the global structure of the magnetosphere to the current density flowing through the polar cap cascades. We argue that for most pulsars stationary cascades in the polar cap can not support stationary force-free configurations of the magnetosphere.Comment: 5 pages, 4 figures. Presented at the conference "Isolated Neutron Stars: from the Interior to the Surface", London, April 24-28, 2006; to appear in Astrophysics and Space Science. Significantly revised version, a mistake found by ourselfs in the numerical code was corrected, all presented results are obtained with the correct version of the cod

Characteristics of the amino acid composition of flour types for gluten-free pasta production

Research on the study of the formulation of gluten-free pasta and the selection of raw materials for their production, depending on the amino acid composition, is necessary for the prevention and treatment of diseases such as phenylketonuria and celiac disease, non-celiac non-allergic sensitivity. In the world it occurs with a frequency of 1: 100. More than 472 people are registered in Kazakhstan. Wheat gliadin is characterized by a deficient content of essential amino acids: methionine, cysteine, threonine, tryptophan, arginine, histidine, especially limiting lysine. However, wheat contains non-essential amino acids (glutamic acid, proline in an amount of 16-44 %), which have the ability to be synthesized in the human body, have a toxic effect on people with signs of gluten intolerance. For the treatment and prevention of these diseases, the gluten content should not exceed 20 ppm/kg of the consumed product. The only way out for all patients, except for the treatment of comorbidities, is the observance of a strict gluten-free diet. Gluten-free types of flour from corn and rice do not contain the necessary amounts of essential amino acids, in particular lysine. Legume proteins, including chickpeas, are well balanced in terms of amino acid composition compared to cereal proteins. It has been determined that food sorghum contains all the basic substances necessary for normal human life: proteins from 11-16 %, including lysine 0.17 % - 0.33 %, starch from 60 - 66 %, fat up to 5,5 %.   Purpose: selection of cereals and legumes by amino acid composition for the production of gluten-free pasta.   The resarch of the amino acid composition of the studied types of flour showed that the combined use of gluten-free buckwheat, corn, rice flour in various compositions and ratios with sorghum or chickpea flour increases the nutritional value of gluten-free pasta products

Bottom topography, length, chamber structure of timergazin canyon-like valley and problems of oil and gas exploration in basement

In this article there are specified: a sub-latitudinal valley bottom topography of South Tatar arch, valley length and a position of directive pallial-crustal first order fracture. The valley bottom chamber was considered as continental rift structure with fracture-block tectonics in plan. The possible contribution of the valley to hydrocarbon transit from deep formations is estimated. The Subkhankulovsky swell is specified as possible hydrocarbon deposit within the basement. © 2009

Constraining gamma-ray pulsar gap models with a simulated pulsar population

With the large sample of young gamma-ray pulsars discovered by the Fermi Large Area Telescope (LAT), population synthesis has become a powerful tool for comparing their collective properties with model predictions. We synthesised a pulsar population based on a radio emission model and four gamma-ray gap models (Polar Cap, Slot Gap, Outer Gap, and One Pole Caustic) normalizing to the number of detected radio pulsars in select group of surveys. The luminosity and the wide beams from the outer gaps can easily account for the number of Fermi detections in 2 years of observations. The wide slot-gap beams requires an increase by a factor of ~10 of the predicted luminosity to produce a reasonable number of gamma-ray pulsars. Such large increases in the luminosity may be accommodated by implementing offset polar caps. The narrow polar-cap beams contribute at most only a handful of LAT pulsars. Standard distributions in birth location and pulsar spin-down power (Edot) fail to reproduce the LAT findings: all models under-predict the number of LAT pulsars with high Edot, and they cannot explain the high probability of detecting both the radio and gamma-ray beams at high Edot. The beaming factor remains close to 1 over 4 decades in Edot evolution for the slot gap whereas it significantly decreases with increasing age for the outer gaps. The evolution of the slot-gap luminosity with Edot is compatible with the large dispersion of gamma-ray luminosity seen in the LAT data. The stronger evolution predicted for the outer gap, which is linked to the polar cap heating by the return current, is apparently not supported by the LAT data. The LAT sample of gamma-ray pulsars therefore provides a fresh perspective on the early evolution of the luminosity and beam width of the gamma-ray emission from young pulsars, calling for thin and more luminous gaps.Comment: 23 pages, 21 figures, accepted for publication in A&

Mechanisms for High-frequency QPOs in Neutron Star and Black Hole Binaries

We explain the millisecond variability detected by Rossi X-ray Timing Explorer (RXTE) in the X-ray emission from a number of low mass X-ray binary systems (Sco X-1, 4U1728-34, 4U1608-522, 4U1636-536, 4U0614+091, 4U1735-44, 4U1820-30, GX5-1 and etc) in terms of dynamics of the centrifugal barrier, a hot boundary region surrounding a neutron star. We demonstrate that this region may experience the relaxation oscillations, and that the displacements of a gas element both in radial and vertical directions occur at the same main frequency, of order of the local Keplerian frequency. We show the importance of the effect of a splitting of the main frequency produced by the Coriolis force in a rotating disk for the interpretation of a spacing between the QPO peaks. We estimate a magnitude of the splitting effect and present a simple formula for the whole spectrum of the split frequencies. It is interesting that the first three lowest-order overtones fall in the range of 200-1200 Hz and match the kHz-QPO frequencies observed by RXTE. Similar phenomena should also occur in Black Hole (BH) systems, but, since the QPO frequency is inversely proportional to the mass of a compact object, the frequency of the centrifugal-barrier oscillations in the BH systems should be a factor of 5-10 lower than that for the NS systems. The X-ray spectrum formed in this region is a result of upscattering of a soft radiation (from a disk and a NS surface) off relatively hot electrons in the boundary layer. We also briefly discuss some alternative QPO models, including a possibility of acoustic oscillations in the boundary layer, the proper stellar rotation, and g-mode disk oscillations.Comment: The paper is coming out in the Astrophysical Journal in the 1st of May issue of 199

The acid-base properties and the complexation of tributyl [aminotris(methylenephosphonic acid)] in aqueous solution

© 2016 Taylor & Francis Group, LLC.The acid-base and complexing properties of tributyl [aminotris(methylenephosphonic acid)] (H3L) with divalent metals were investigated in aqueous solution via the potentiometric titration method. The formation of 1:1 species partially protonated [MH2L] and totally deprotonated [ML−] as well as hydroxo species [M(OH)L2−] has been established