Reconnecting Magnetic Flux Tubes as a Source of In Situ Acceleration in Extragalactic Radio Sources

Many extended extragalactic radio sources require a local {\it in situ\/} acceleration mechanism for electrons, in part because the synchrotron lifetimes are shorter than the bulk travel time across the emitting regions. If the magnetic field in these sources is localized in flux tubes, reconnection may occur between regions of plasma \be (ratio of particle to magnetic pressure) $<<1$, even though $\beta$ averaged over the plasma volume may be \gsim 1. Reconnection in low $\beta$ regions is most favorable to acceleration from reconnection shocks. The reconnection X-point regions may provide the injection electrons for their subsequent non-thermal shock acceleration to distributions reasonably consistent with observed spectra. Flux tube reconnection might therefore be able to provide $in\ situ$ acceleration required by large scale jets and lobes.Comment: 14 pages, plain TeX, accepted to Ap.J.Let

Dialogical organics of pedagogical discourse: linguo-pragmatic aspect

The article discusses the basic dialogue properties; it is particularly emphasized that the problems of studying the text, discourse and language of the operationalterminological apparatus are connected with the discursive concept of dialogis

Conductivity, weak ferromagnetism and charge instability in α−MnS\alpha-MnS single crystal

The temperature dependence of resistivity, magnetization and electron-spin resonance of the $\alpha- MnS$ single crystal were measured in temperature range of $5 K < T < 550 K$. Magnetization hysteresis in applied magnetic field up to 0.7 T at $T=5 K, 77 K, 300 K$, irreversible temperature behavior of magnetization and resistivity were found . The obtained data were explained in terms of degenerate tight binding model using random phase approximation. The contribution of holes in $t_{2g}$ and $e_g$ bands of manganese ions to the conductivity, optical absorbtion spectra and charge instability in $\alpha -MnS$ were studied. Charge susceptibility maxima resulted from the competition of the on-site Coulomb interaction between the holes in different orbitals and small hybridization of sub-bands were calculated at $T=160 K, 250 K, 475 K$.Comment: 6 pages, 12 figure

Battle of Stalingrad in the diaries of junior lieutenant Rudnitsky

The authors of the article examine the events of the Battle of Stalingrad through the prism of the diary entries of Junior Lieutenant Z.S. Rudnitsky. The authors set themselves a number of tasks for revealing the topic: to show the role of air defense and its contribution to the victory at Stalingrad; evaluate the level of material and technical supply of the Red Army, evaluate the value of front-line diaries as a historical source. The relevance of this topic is explained by the need to understand the processes that resulted in the greatest military victory of World War II, as well as the increased interest in diaries as a historical source, which researchers attribute to the so-called soft communicative memory. The novelty of the study is the introduction into the scientific circulation of a previously unknown source the front-line diary of Z.S. Rudnitsky, which he led throughout the battle of Stalingrad. The value of the present source lies in the display of direct perception of the war through the eyes of a young nineteen-year-old lieutenant. Working with the materials of diary entries allowed to deepen our ideas about supplying and arming the defenders of Stalingrad, their moral condition, domestic problems. The study was carried out as part of the problem field of memory studies using retrospective, comparative historical, interdisciplinary methods. Based on an analysis of everyday life of the front lieutenant Rudnitsky, who fought on the Stalingrad front as part of the 303 artillery-anti-aircraft regiment, it was concluded that the daily military feat of the anti-aircraft gunners made it possible to block the sky over the city for German aviation, especially during the counteroffensive. The value of this feat becomes even more obvious against the background of an extremely difficult state and a lack of machinery, equipment, household inconveniences. It is concluded that it is necessary to introduce into the scientific circulation diaries that significantly expand the range of historical sources

Particle Acceleration and Magnetic Dissipation in Relativistic Current Sheet of Pair Plasmas

We study linear and nonlinear development of relativistic and ultrarelativistic current sheets of pair plasmas with antiparallel magnetic fields. Two types of two-dimensional problems are investigated by particle-in-cell simulations. First, we present the development of relativistic magnetic reconnection, whose outflow speed is an order of the light speed c. It is demonstrated that particles are strongly accelerated in and around the reconnection region, and that most of magnetic energy is converted into "nonthermal" part of plasma kinetic energy. Second, we present another two-dimensional problem of a current sheet in a cross-field plane. In this case, the relativistic drift kink instability (RDKI) occurs. Particle acceleration also takes place, but the RDKI fast dissipates the magnetic energy into plasma heat. We discuss the mechanism of particle acceleration and the theory of the RDKI in detail. It is important that properties of these two processes are similar in the relativistic regime of T > mc^2, as long as we consider the kinetics. Comparison of the two processes indicates that magnetic dissipation by the RDKI is more favorable process in the relativistic current sheet. Therefore the striped pulsar wind scenario should be reconsidered by the RDKI.Comment: To appear in ApJ vol. 670; 60 pages, 27 figures; References and typos are fixe

Winds, B-Fields, and Magnetotails of Pulsars

We investigate the emission of rotating magnetized neutron stars due to the acceleration and radiation of particles in the relativistic wind and in the magnetotail of the star. We consider that the charged particles are accelerated by driven collisionless reconnection. Outside of the light cylinder, the star's rotation acts to wind up the magnetic field to form a predominantly azimuthal, slowly decreasing with distance, magnetic field of opposite polarity on either side of the equatorial plane normal to the star's rotation axis. The magnetic field annihilates across the equatorial plane with the magnetic energy going to accelerate the charged particles to relativistic energies. For a typical supersonically moving pulsar, the star's wind extends outward to the standoff distance with the interstellar medium. At larger distances, the power output of pulsar's wind $\dot{E}_w$ of electromagnetic field and relativistic particles is {\it redirected and collimated into the magnetotail} of the star. In the magnetotail it is proposed that equipartition is reached between the magnetic energy and the relativistic particle energy. For such conditions, synchrotron radiation from the magnetotails may be a significant fraction of $\dot{E}_w$ for high velocity pulsars. An equation is derived for the radius of the magnetotail $r_m(z^\prime)$ as a function of distance $z^\prime$ from the star. For large distances $z^\prime$, of the order of the distance travelled by the star, we argue that the magnetotail has a `trumpet' shape owing to the slowing down of the magnetotail flow.Comment: 11 pages, 4 figures, accepted for publication in Ap

Strongly anisotropic magnetocaloric effect in a dipolar magnet LiGdF4_4

We report the detailed study of the magnetocaloric effect (MCE) in a dipolar-Heisenberg magnet LiGdF$_4$ using magnetization measurements performed on a single crystal sample. Entropy variation on isothermal demagnetization from the magnetic field up to 3 T is determined in the temperature range 2-10 K for two principal directions of the applied field (parallel and perpendicular to the tetragonal $c$-axis of the crystal). The MCE is found to be highly anisotropic, with the cooling efficiency being up to twice higher at $H\parallel c$. The results are nicely interpreted in the frame of a conventional molecular field approach taking into account considerable anisotropy of the paramagnetic Curie-Weiss temperature. These results are compared to earlier studies of MCE in powder samples of LiGdF$_4$ [T. Numazawa et al., AIP Conf. Proc. 850, 1579 (2006)] as well as with analogous data for other well known magnetocaloric materials. Our findings may open new possibilities to enhance the efficiency of magnetic refrigeration in the liquid helium-4 temperature range.Comment: 4 pages, 3 figure

Superconducting properties of sulfur-doped iron selenide

The recent discovery of high-temperature superconductivity in single-layer iron selenide has generated significant experimental interest for optimizing the superconducting properties of iron-based superconductors through the lattice modification. For simulating the similar effect by changing the chemical composition due to S doping, we investigate the superconducting properties of high-quality single crystals of FeSe$_{1-x}$S$_{x}$ ($x$=0, 0.04, 0.09, and 0.11) using magnetization, resistivity, the London penetration depth, and low temperature specific heat measurements. We show that the introduction of S to FeSe enhances the superconducting transition temperature $T_{c}$, anisotropy, upper critical field $H_{c2}$, and critical current density $J_{c}$. The upper critical field $H_{c2}(T)$ and its anisotropy are strongly temperature dependent, indicating a multiband superconductivity in this system. Through the measurements and analysis of the London penetration depth $\lambda _{ab}(T)$ and specific heat, we show clear evidence for strong coupling two-gap $s$-wave superconductivity. The temperature-dependence of $\lambda _{ab}(T)$ calculated from the lower critical field and electronic specific heat can be well described by using a two-band model with $s$-wave-like gaps. We find that a $d$-wave and single-gap BCS theory under the weak-coupling approach can not describe our experiments. The change of specific heat induced by the magnetic field can be understood only in terms of multiband superconductivity.Comment: 13 pages, 7 figure

Mordovo-Karmalskoye Field: The Bitumen Composition in Productive Strata after Passing of the Combustion Front in Well

The specific features of the composition of both natural bitumens of the Mordovo-Karmalskoye field and products of the bitumen thermal transformation in strata after passing of the combustion front in a well are studied. The composition of organic matter and its bitumen components left in reservoir after passing of the combustion front and the parameters of bitumen which underwent no artificial impact are compared. The combustion is found to cause the deep transformations in the bitumen composition and the differentiation of bitumen properties through a cross section. The rather light bitumen (density is equal to 0,94 g/cm3) is in the low concentration in the roof part of stratum. A content of paraffin-naphtene hydrocarbons, particularly nalkanes, increases in the hydrocarbon part of bitumen. Accordingly to the group and hydrocarbon compositions, the elemental composition is altered, the hydrogen content increases and the sulphur content decreases. Contrarily, the bitumen in the combustion interval is heavier (1,013 g/cm3). A quality of the bitumen is minimal there. The interlayers having an enhanced content of the insoluble organic compounds are found. The high content of asphaltenes causes the low hydrogen content and the high carbon content in the bitumen composition. All these parameters are abnormal if to compare with the ordinary, non-transformed bitumens of the Mordovo-Karmalskoye field. In the lower part of cross section underwent no combustion, the content and composition of bitumen become ordinary for the productive thickness. At the same time, the lower oil content and the higher content of asphaltenes and sulphur in bitumens are an evidence to the displacement of light to the productive wells hydrocarbons simultaneously to passing of the combustion front. That confirms the earlier observed fact that the oil is produced at the part of reservoir which underwent no in situ combustion. In addition to the alterations in the organic matter composition and content, the bitumen-bearing rocks are also transformed, particularly a ratio between iron(II), iron(III) compounds and pyrite is changed. The revealed factors which effect the quality of recovered bitumens and the alterations in the mineralogy make possible to control the temperature regime and passing of the combustion front

"Propeller" Regime of Disk Accretion to Rapidly Rotating Stars

We present results of axisymmetic magnetohydrodynamic simulations of the interaction of a rapidly-rotating, magnetized star with an accretion disk. The disk is considered to have a finite viscosity and magnetic diffusivity. The main parameters of the system are the star's angular velocity and magnetic moment, and the disk's viscosity, diffusivity. We focus on the "propeller" regime where the inner radius of the disk is larger than the corotation radius. Two types of magnetohydrodynamic flows have been found as a result of simulations: "weak" and "strong" propellers. The strong propeller is characterized by a powerful disk wind and a collimated magnetically dominated outflow or jet from the star. The weak propeller have only weak outflows. We investigated the time-averaged characteristics of the interaction between the main elements of the system, the star, the disk, the wind from the disk, and the jet. Rates of exchange of mass and angular momentum between the elements of the system are derived as a function of the main parameters. The propeller mechanism may be responsible for the fast spinning-down of the classical T Tauri stars in the initial stages of their evolution, and for the spinning-down of accreting millisecond pulsars.Comment: 18 pages, 16 figures, ApJ (accepted), added references, corrected typos; see animation at http://astrosun2.astro.cornell.edu/us-rus/disk_prop.ht