Proton acceleration in analytic reconnecting current sheets

Particle acceleration provides an important signature for the magnetic collapse that accompanies a solar flare. Most particle acceleration studies, however, invoke magnetic and electric field models that are analytically convenient rather than solutions of the governing magnetohydrodynamic equations. In this paper a self-consistent magnetic reconnection solution is employed to investigate proton orbits, energy gains, and acceleration timescales for proton acceleration in solar flares. The magnetic field configuration is derived from the analytic reconnection solution of Craig and Henton. For the physically realistic case in which magnetic pressure of the current sheet is limited at small resistivities, the model contains a single free parameter that specifies the shear of the velocity field. It is shown that in the absence of losses, the field produces particle acceleration spectra characteristic of magnetic X-points. Specifically, the energy distribution approximates a power law ~ξ-3/2 nonrelativistically, but steepens slightly at the higher energies. Using realistic values of the “effective” resistivity, we obtain energies and acceleration times that fall within the range of observational data for proton acceleration in the solar corona

Hall current effects in dynamic magnetic reconnection solutions

The impact of Hall current contributions on flow driven planar magnetic merging solutions is discussed. The Hall current is important if the dimensionless Hall parameter (or normalized ion skin depth) satisfies cH>η where η is the inverse Lundquist number for the plasma. A dynamic analysis of the problem shows, however, that the Hall current initially manifests itself, not by modifying the planar reconnection field, but by inducing a non-reconnecting perpendicular "separator" component in the magnetic field. Only if the stronger condition c2/H > η is satisfied can Hall currents be expected to affect the planar merging. These analytic predictions are then tested by performing a series of numerical experiments in periodic geometry, using the full system of planar magnetohydrodynamic (MHD) equations. The numerical results confirm that the nature of the merging changes dramatically when the Hall coupling satisfies c2/H > η. In line with the analytic treatment of sheared reconnection, the coupling provided by the Hall term leads to the emergence of multiple current layers that can enhance the global Ohmic dissipation at the expense of the reconnection rate. However, the details of the dissipation depend critically on the symmetries of the simulation, and when the merging is "head-on" (i.e., comprises fourfold symmetry) the reconnection rate can be enhanced

Acesso das pequenas empresas russas aos mercados de contratos públicos: análise de dados

The aim of this study was to assess the current extent of participation by Russian small enterprises in regional public procurement. We discussed how legislation affects the volume of contracts awarded to small enterprises. We calculated the number of contracts per 100 small enterprises, how much the number and value of such contracts account for in the total number and value of contracts concluded with all suppliers per region, as well as what is the average value of contracts per small enterprise and the average value of one such contract. In order to ensure benchmarking for enterprises located in different regions, such enterprises were assessed on the basis of relative indicators. This study used official statistics accumulated with regard to all public procurement in the regions. The data on the number of contracts and their value for the period from 2010 to 2014 were used. For the purposes of empirical data analysis, the normal distribution probability density functions set for all the indicators in question were used. The findings of this study and the tools used for assessing the extent of participation by small enterprises in public procurement can be used when researching entrepreneurship, as well as to justify the contract system development programs in Russia. Such information is important for entrepreneurs, as it enables them to assess the feasibility and consequences of participation in public procurement.El objetivo de este estudio fue evaluar el grado actual de participación de las pequeñas empresas rusas en la contratación pública regional. Discutimos cómo la legislación afecta el volumen de contratos adjudicados a pequeñas empresas. Calculamos el número de contratos por cada 100 pequeñas empresas, cuánto representan el número y el valor de dichos contratos en el número y el valor total de los contratos celebrados con todos los proveedores por región, así como también cuál es el valor promedio de los contratos por cada pequeña empresa y el valor promedio de uno de esos contratos. Con el fin de garantizar la evaluación comparativa para las empresas ubicadas en diferentes regiones, dichas empresas se evaluaron sobre la base de indicadores relativos. Este estudio utilizó estadísticas oficiales acumuladas con respecto a todas las contrataciones públicas en las regiones. Se utilizaron los datos sobre el número de contratos y su valor para el período de 2010 a 2014. A los efectos del análisis de datos empíricos, se utilizaron las funciones de densidad de probabilidad de distribución normal establecidas para todos los indicadores en cuestión. Las conclusiones de este estudio y las herramientas utilizadas para evaluar el grado de participación de las pequeñas empresas en la contratación pública se pueden utilizar al investigar el espíritu empresarial, así como para justificar los programas de desarrollo de sistemas contractuales en Rusia. Dicha información es importante para los empresarios, ya que les permite evaluar la viabilidad y las consecuencias de la participación en la contratación pública.O objetivo deste estudo foi avaliar o atual grau de participação das pequenas empresas russas nas compras públicas regionais. Discutimos como a legislação afeta o volume de contratos concedidos a pequenas empresas. Nós calculamos o número de contratos por 100 pequenas empresas, que representam o número eo valor desses contratos no número total eo valor total dos contratos com todos os fornecedores por região, bem como o que o valor médio de contratos para cada empresa de pequeno porte e o valor médio de um desses contratos. Para garantir benchmarking para empresas localizadas em diferentes regiões, essas empresas foram avaliadas com base em indicadores relativos. Este estudo utilizou estatísticas oficiais acumuladas em relação a todas as compras públicas nas regiões. Foram utilizados os dados sobre o número de contratos e seu valor para o período de 2010 a 2014. Para fins de análise empírica dos dados, foram utilizadas as funções de densidade de probabilidade de distribuição normal estabelecidas para todos os indicadores em questão. As conclusões deste estudo e os instrumentos utilizados para avaliar o grau de participação das pequenas empresas nos contratos públicos podem ser utilizados na investigação do empreendedorismo, bem como para justificar os programas de desenvolvimento de sistemas contratuais na Rússia. Esta informação é importante para os empresários, pois permite avaliar a viabilidade e as consequências da participação em contratos públicos

Indeterminacy and instability in Petschek reconnection

We explain two puzzling aspects of Petschek's model for fast reconnection. One is its failure to occur in plasma simulations with uniform resistivity. The other is its inability to provide anything more than an upper limit for the reconnection rate. We have found that previously published analytical solutions based on Petschek's model are structurally unstable if the electrical resistivity is uniform. The structural instability is associated with the presence of an essential singularity at the X-line that is unphysical. By requiring that such a singularity does not exist, we obtain a formula that predicts a specific rate of reconnection. For uniform resistivity, reconnection can only occur at the slow, Sweet-Parker rate. For nonuniform resistivity, reconnection can occur at a much faster rate provided that the resistivity profile is not too flat near the X-line. If this condition is satisfied, then the scale length of the nonuniformity determines the reconnection rate

Ferrite-damped higher-order mode study in the Brookhaven energy-recovery linac cavity

A superconducting energy-recovery linac (ERL) is under construction at Brookhaven National Laboratory (BNL) to serve as a test bed for an application to upgrades of the Relativistic Heavy Ion Collider (RHIC). The damping of higher-order modes in the superconducting five-cell cavity is of paramount importance and represents the topic of this paper. Achieving the damping by the exclusive use of two ferrite absorbers and the adoption of a space-saving step instead of the conventional taper are part of the exploratory study. Absorber properties which are portable to simulation programs for the ERL cavity have been obtained by measuring the absorber as a ferrite-loaded pill-box cavity. Measured and simulated results for the lowest dipole modes in the prototype copper cavity with one absorber are discussed. First room-temperature measurements of the fully assembled niobium cavity string are presented which confirm the effective damping of higher-order modes by the ferrite absorbers, and which give credibility to the simulated R over Q's in the ERL.open1

Avaliação dos aspectos financeiros das pequenas e médias empresas: experiência russa

The aim of this study was to assess the key financials of an array of micro-sized businesses, small and medium-sized enterprises as grouped by industry. This article deals with the assessment results of such financials as the net financial result of enterprises, the proportion of profitable and loss-making enterprises, the profitability of manufactured and sold products, the current levels of profit and loss, respectively, per profitable and loss-making enterprise. The dynamics of such financials during the period from 2010 to 2014 was presented. Accounting and statistical reporting was used as the input data. In the course of this research it was proven that during that period the profitable enterprises accounted for about 80%. However, the level of profitability did not depend on the size of an enterprise. The largest proportion of profitable enterprises was noted in such sectors as education and commerce. The net financial result per employee in micro-enterprises was significantly higher than those for medium-sized enterprises and small enterprises. The results of this study may be used to validate business development plans and programs for various regions and sectors of the Russian economy. El objetivo de este estudio fue evaluar las finanzas clave de una serie de pequeñas empresas, pequeñas y medianas empresas agrupadas por industria. Este artículo trata de los resultados de la evaluación de tales finanzas como el resultado financiero neto de las empresas, la proporción de empresas rentables y que generan pérdidas, la rentabilidad de los productos fabricados y vendidos, los niveles actuales de ganancias y pérdidas, respectivamente, por rentabilidad y pérdida empresa de creación. La dinámica de tales finanzas durante el período 2010-2014 se presentó. Los informes contables y estadísticos se usaron como datos de entrada. En el curso de esta investigación, se comprobó que durante ese período las empresas rentables representaron aproximadamente el 80%. Sin embargo, el nivel de rentabilidad no depende del tamaño de una empresa. La mayor proporción de empresas rentables se observó en sectores como la educación y el comercio. El resultado financiero neto por empleado en las microempresas fue significativamente mayor que el de las medianas y pequeñas empresas. Los resultados de este estudio pueden usarse para validar planes y programas de desarrollo comercial para diversas regiones y sectores de la economía rusa. O objetivo deste estudo foi avaliar as principais finanças de uma série de microempresas, pequenas e médias empresas agrupadas por setor. Este artigo trata dos resultados da avaliação de tais finanças como o resultado financeiro líquido das empresas, a proporção de empresas lucrativas e deficitárias, a rentabilidade dos produtos fabricados e vendidos, os níveis atuais de lucros e perdas, respectivamente, por lucro e perda empresa de fabricação. A dinâmica de tais finanças durante o período de 2010 a 2014 foi apresentada. Relatórios contábeis e estatísticos foram usados como dados de entrada. No decorrer desta pesquisa, ficou provado que, durante esse período, as empresas lucrativas representavam cerca de 80%. No entanto, o nível de lucratividade não dependia do tamanho de uma empresa. A maior proporção de empresas lucrativas foi observada em setores como educação e comércio. O resultado financeiro líquido por empregado nas microempresas foi significativamente superior ao das médias empresas e pequenas empresas. Os resultados deste estudo podem ser usados para validar planos e programas de desenvolvimento de negócios para várias regiões e setores da economia russa

Analysis of the rotation period of asteroids (1865) Cerberus, (2100) Ra-Shalom, and (3103) Eger - search for the YORP effect

The spin state of small asteroids can change on a long timescale by the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, the net torque that arises from anisotropically scattered sunlight and proper thermal radiation from an irregularly-shaped asteroid. The secular change in the rotation period caused by the YORP effect can be detected by analysis of asteroid photometric lightcurves. We analyzed photometric lightcurves of near-Earth asteroids (1865) Cerberus, (2100) Ra-Shalom, and (3103) Eger with the aim to detect possible deviations from the constant rotation caused by the YORP effect. We carried out new photometric observations of the three asteroids, combined the new lightcurves with archived data, and used the lightcurve inversion method to model the asteroid shape, pole direction, and rotation rate. The YORP effect was modeled as a linear change in the rotation rate in time d\omega /dt. Values of d\omega/ dt derived from observations were compared with the values predicted by theory. We derived physical models for all three asteroids. We had to model Eger as a nonconvex body because the convex model failed to fit the lightcurves observed at high phase angles. We probably detected the acceleration of the rotation rate of Eger d\omega / dt = (1.4 +/- 0.6) x 10^{-8} rad/d (3\sigma error), which corresponds to a decrease in the rotation period by 4.2 ms/yr. The photometry of Cerberus and Ra-Shalom was consistent with a constant-period model, and no secular change in the spin rate was detected. We could only constrain maximum values of |d\omega / dt| < 8 x 10^{-9} rad/d for Cerberus, and |d\omega / dt| < 3 x 10^{-8} rad/d for Ra-Shalom