Locating current sheets in the solar corona

Current sheets are essential for energy dissipation in the solar corona, in particular by enabling magnetic reconnection. Unfortunately, sufficiently thin current sheets cannot be resolved observationally and the theory of their formation is an unresolved issue as well. We consider two predictors of coronal current concentrations, both based on geometrical or even topological properties of a force free coronal magnetic field. First, there are separatrices related to magnetic nulls. Through separatrices the magnetic connectivity changes discontinuously. Coronal magnetic nulls are, however, very rare. At second, inspired by the concept of generalized magnetic reconnection without nulls, quasi-separatrix layers (QSL) were suggested. Through QSL the magnetic connectivity changes continuously, though strongly. The strength of the connectivity change can be quantified by measuring the squashing of the flux tubes which connect the magnetically conjugated photospheres. We verify the QSL and separatrix concepts by comparing the sites of magnetic nulls and enhanced squashing with the location of current concentrations in the corona. Due to the known difficulties of their direct observation we simulated the coronal current sheets by numerically calculating the response of the corona to energy input from the photosphere heating a simultaneously observed EUV Bright Point. We did not find coronal current sheets not at the separatrices but at several QSL locations. The reason is that although the geometrical properties of force free extrapolated magnetic fields can indeed, hint at possible current concentrations, a necessary condition for current sheet formation is the local energy input into the corona

Electric current circuits in astrophysics

Cosmic magnetic structures have in common that they are anchored in a dynamo, that an external driver converts kinetic energy into internal magnetic energy, that this magnetic energy is transported as Poynting fl ux across the magnetically dominated structure, and that the magnetic energy is released in the form of particle acceleration, heating, bulk motion, MHD waves, and radiation. The investigation of the electric current system is particularly illuminating as to the course of events and the physics involved. We demonstrate this for the radio pulsar wind, the solar flare, and terrestrial magnetic storms

Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011

Application of the Silicon Photomultipliers for Detectors in the GlueX Experiment

AbstractThe GlueX detector in Hall D at Jefferson Lab [1]is instrumented with about 5000 Silicon Photomultipliers (SiPM) manufactured by Hamamatsu Corporation [2]. These photo sensors have properties similar to conventional photomultipliers but can be operated at high magnetic fields. Silicon photomultipliers with a sensitive area of 3x3 mm2 are used to detect light from the following GlueX scintillator detectors: the tagger microscope, pair spectrometer, and start counter. Arrays of 4x4 SiPMs sensors were chosen for the instrumentation of the barrel electromagnetic calorimeter. The tagger microscope must operate at high rates (up to 2.5MHz) and provide time measurements with a resolution better than 0.3ns. The paper will describe some results of the characterization of SiPMs for various GlueX sub-detectors

Features of knowledge representation in the decision support system

Рассматриваются процесс принятия решений с использованием теории нечетких множеств, система поддержки принятия решений в соответствии с логико-лингвистическим подходомРозглядається процес прийняття рішень з використанням теорії нечітких множин, система підтримки прийняття рішень відповідно з логіко - лінгвістичним підходомThe decision - making process with the use of the theory of indistinct sets, and the decision support system pursuant to the logical - linguistic approach are considered in the articl

Algorithm for finding cyclic code that satisfies the specified accuracy

Розглянуто алгебраїчна структура циклічних кодів, їх властивості та характеристики. Запропонований процес алгоритмізації циклічного коду, який задовольняє заданій точності.Рассмотрены алгебраическая структура циклических кодов, их свойства и характеристики. Предложен процесс алгоритмизации циклического кода, который удовлетворяет заданной точности.The algebraic structure of cyclic codes, their properties and characteristics. We propose a process algorithmization cyclic code which satisfies a predetermined fidelity

Composition and thermal structure of the lithospheric mantle beneath kimberlite pipes from the Catoca cluster, Angola

Garnet, clinopyroxene and ilmenite xenocrysts from three Angolan kimberlite pipes belonging to the Catoca cluster (Angola Caquele, Camitongo I and II, and Catoca) from the SW part of the Congo-Kasai craton, reveal similar features which suggest a similarity of mantle structure. PT estimates for pyropes, Cr-diopsides and picroilmenites reveal similar geothermal conditions of ~ 37 - 40 mW/m2. This is slightly higher than the values determined for the Catoca pipe. Higher temperature conditions ~ 45 mW/m2 were determined for low-Cr pyroxenes and omphacites. The similar general mineralogy and suggested mantle lithology, as well as reconstructed layering of the sub-continental lithospheric mantle (SCLM), are similar for Camitongo I-II as well as for Caquele and Catoca pipes. Heating at depths of 7.5-4.5 GPa (240-140 km) is a general feature of the SCLM beneath the field. The high temperature trend for low-Cr and hybrid pyroxenes from the base of the SCLM up to 30 GPa (100 km) represents the PT path of the protokimberlite melts. PT conditions for ilmenites mainly correspond to colder conditions of crystallization in wall rocks and the outer parts of magmatic channels. Individual geochemical features of the minerals for each SCLM suggest pervasive metasomatism in lower part of the SCLM. Clinopyroxene trace element patterns from the Caquele pipe reveal a lherzolitic affinity; they are LILE-enriched with Ba peaks due to phlogopite melting, while those from Camitongo I-II show Ta-Nb enrichment and Pb troughs. The ilmenite trends trace the mantle column from deep to shallow mantle, evolving to Fe-ilmenites due to advanced AFC of protokimberlite magma that also produced abundant Fe-rich clinopyroxenes. The rise of calculated fO2 correlates with the position of protokimberlites. Comparison with the thermal gradient derived from peridotitic inclusions from Catoca cluster is lower then for Lesotho possibly related to the thicker lithospheric roots beneath the Congo-Kasai craton

Evaluation of symmetric digital recursive filter prediction

В статье рассмотрен вопрос повышения эффективности нерекурсивных цифровых фильтров предсказания по критерию минимума среднеквадратичной ошибки. Показывается, что для стационарных и неста-ционарных случайных процессов большую точность оценки обеспечивает фильтр с симметричной импульсной характеристикой.У статті розглянуто питання підвищення ефективності нерекурсивних цифрових фільтрів передбачення за критерієм мінімуму середньоквадратичної помилки. Показується, що для стаціонарних і нестаціонарних випадкових процесів більшу точність оцінки забезпечує фільтр із симетричною імпульсною характеристикою.The article deals with the issue of increasing the efficiency of non-recursive digital filter prediction of the criterion of minimum mean squared error. It is shown that for stationary and non-stationary random processes more accurate assessment provides a filter with a symmetric impulse response

The use of graphene in microelectronics for the heat sink

Розглянуті основні властивості графена та технології його отримання. Показано, що на даний час результати наукових дослідів та промислові розробки дозволяють запропонувати застосування графена як матеріалу для тепловідведення в мікроелектроніці, що збільшить щільність упакування елементів в мікросхемах.Рассмотрены основные свойства графена и технологии его получения. Показано, что на данное время результаты научных исследований и промышленные разработки позволяют предложить, что графен как материал можно использовать для теплоотвода в микроэлектронике, что позволит увеличить плотность упаковки элементов в микросхемах.The article describes the basic properties of graphene and its production technology. It is shown that at this time the results of scientific research and industrial development allow us to offer that graphene as a material can be used for heat dissipation in microelectronics, which will increase the packing density of elements in the chips