Formation of "Lightnings" in a Neutron Star Magnetosphere and the Nature of RRATs

The connection between the radio emission from "lightnings" produced by the absorption of high-energy photons from the cosmic gamma-ray background in a neutron star magnetosphere and radio bursts from rotating radio transients (RRATs) is investigated. The lightning length reaches 1000 km; the lightning radius is 100 m and is comparable to the polar cap radius. If a closed magnetosphere is filled with a dense plasma, then lightnings are efficiently formed only in the region of open magnetic field lines. For the radio emission from a separate lightning to be observed, the polar cap of the neutron star must be directed toward the observer and, at the same time, the lightning must be formed. The maximum burst rate is related to the time of the plasma outflow from the polar cap region. The typical interval between two consecutive bursts is ~100 s. The width of a single radio burst can be determined both by the width of the emission cone formed by the lightning emitting regions at some height above the neutron star surface and by a finite lightning lifetime. The width of the phase distribution for radio bursts from RRATs, along with the integrated pulse width, is determined by the width of the bundle of open magnetic field lines at the formation height of the radio emission. The results obtained are consistent with the currently available data and are indicative of a close connection between RRATs, intermittent pulsars, and extreme nullers.Comment: 24 pages, no figures, references update

Pulsar death line revisited -- II. 'The death valley'

In this paper, which is the second in a series of papers, we analyse what parameters can determine the width of the radio pulsar 'death valley' in the $P$-${\dot P}$ diagram. Using exact expression for the maximum potential drop, which can be realised over magnetic polar caps and the corresponding threshold for the secondary plasma production determined in Paper I, we analyse in detail the observed distribution of pulsars taking into account all the possible parameters (radius $R$ and moment of inertia of a neutron star $I_{\rm r}$, high-energy tail in the $\gamma$-quanta energy distribution giving rise to secondary particles, etc.) which could broaden 'the death line'. We show that the consistent allowance for all these effects leads to a sufficiently wide of 'the death valley' containing all the observed pulsars even for dipole magnetic field of a neutron star.Comment: 9 pages, 4 figures, submitted to MNRA

3D Relativistic Magnetohydrodynamic Simulations of Magnetized Spine-Sheath Relativistic Jets

Numerical simulations of weakly magnetized and strongly magnetized relativistic jets embedded in a weakly magnetized and strongly magnetized stationary or weakly relativistic (v = c/2) sheath have been performed. A magnetic field parallel to the flow is used in these simulations performed by the new GRMHD numerical code RAISHIN used in its RMHD configuration. In the numerical simulations the Lorentz factor $\gamma = 2.5$ jet is precessed to break the initial equilibrium configuration. In the simulations sound speeds are $\lesssim c/\sqrt 3$ in the weakly magnetized simulations and $\lesssim 0.3c$ in the strongly magnetized simulations. The Alfven wave speed is $\lesssim 0.07c$ in the weakly magnetized simulations and $\lesssim 0.56c$ in the strongly magnetized simulations. The results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized relativistic magnetohydrodynamic (RMHD) equations capable of describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized relativistically moving sheath. The theoretical dispersion relation allows investigation of effects associated with maximum possible sound speeds, Alfven wave speeds near light speed and relativistic sheath speeds. The prediction of increased stability of the weakly magnetized system resulting from c/2 sheath speeds and the stabilization of the strongly magnetized system resulting from c/2 sheath speeds is verified by the numerical simulation results.Comment: 31 pages, 8 figures, accepted for publicatin in ApJ. A paper with high resolution figures available at http://gammaray.nsstc.nasa.gov/~mizuno/research_new.htm

Oxygen diffusion in Sr_0.75Y_0.25CoO_2.625: a molecular dynamics study

Oxygen diffusion in Sr0.75Y0.25CoO2.625 is investigated using molecular dynamics simulations in conjunction with an established set of Born model potentials. We predict an activation energy of diffusion for 1.56 eV in the temperature range of 1000-1400 K. We observe extensive disordering of the oxygen ions over a subset of lattice sites. Furthermore, oxygen ion diffusion both in the a-b plane and along the c axis requires the same set of rate-limiting ion hops. It is predicted that oxygen transport in Sr0.75Y0.25CoO2.625 is therefore isotropic

On the triple pulsar profiles generated by ordinary mode

A detailed study of the refraction of an ordinary wave in the magnetosphere of radio pulsars was carried out. For this, a consistent theory of the generation of secondary particles was constructed, which essentially takes into account the dependence of the number density and the energy spectrum of secondary particles on the distance from the magnetic axis. This made it possible to determine with high accuracy the refraction of the ordinary O-mode in the central region of the outflowing plasma, which makes it possible to explain the central peak of three-humped mean radio profiles. As shown by detailed numerical calculations, in most cases it is possible to reproduce quite well the observed mean profiles of radio pulsars.Comment: 13 pages, 11 figures, 4 tables, accepted by MNRA

Simulation of electromagnetic processes in the grounding system with a short circuit in the operating high-voltage substation

The aim of the work is a test of the developed mathematical model of electromagnetic processes of short circuit and approbation of the created software complex «LiGro» on its basis for the existing grounding system located in three-layer soil. Methodology. To improve the accuracy of calculating the normalized parameters of operating power stations and substations, the authors developed the «LiGro» software package based on the expressions obtained in for calculating the potential of the electric field of a non-equipotential grounding system (GS). To monitor the state and assess the efficiency of the GS of operating power facilities, the electromagnetic diagnostics is used. The topology of the GS was determined with the induction method by complex KNTR-1, the geoelectric structure of the soil was determined by the method of vertical electrical sounding using the Wenner installation, the interpretation of the sounding results was made by the «VEZ-4A» program. The calculation results show that for the selected substation, the model developed in the «LiGro» complex has a deviation δ2 from the experimental values Ut by an average of 8,2 %, and the model implemented in Grounding 1.0 (IEEE model) δ1 is 17,2 %. Originality. The results of the study confirm the adequacy of the developed GS model in the «LiGro» complex based on a three-layer soil model, with the experimental values of the touch voltage obtained by simulating a single-phase ground fault on a real GS in operation. The first time was made approbation of the «LiGro» software package when performing the EMD of the GS of an operating substation with a voltage class of 150 kV. Practical significance. The program software can be used by special measuring’s laboratory to determining electrical safety parameters: touch voltage, GS voltage, and GS resistance. Метою роботи є перевірка розробленої математичної моделі електромагнітних процесів короткого замикання та апробація створеного програмного комплексу «LiGro на її основі для існуючого заземлювального пристрою (ЗП), який розташовано в тришаровому ґрунті. Перевірка практичного застосування була виконана на діючий підстанції класом напруги 150 кВ з використанням вдосконаленої методики електромагнітної діагностики. Топологія ЗП була визначена індукційним методом за допомогою приладу KNTR-1, параметри ґрунту визначені чотириелектродною симетричною установкою за схемою Веннера методом вертикального електричного зондування, інтерпретація результатів зондування виконана спеціалізованою програмою VEZ-4A. Результати порівняння розрахунку показують, що для обраної підстанції модель розроблена в комплексі LiGro має відхилення від експериментальних значень в середньому на 8,2 %, а модель реалізована в Grounding 1.0 (IEEE model) – 17,2 %. Виконано розрахунок нормованих параметрів ЗП в режимі короткого замикання: напругу дотику, опір ЗП та напругу на ЗП. Встановлено, що вони не перевищують допустимого значення. Проаналізовано переваги розрахункового комплексу у порівнянні з аналогами. Отримані результати дозволяють виконати повномасштабне впровадження програмного комплексу в діагностику стану ЗП.&nbsp