3,255 research outputs found
Formation of a rotating jet during the filament eruption on 10-11 April 2013
We analyze multi-wavelength and multi-viewpoint observations of a helically
twisted plasma jet formed during a confined filament eruption on 10-11 April
2013. Given a rather large scale event with its high spatial and temporal
resolution observations, it allows us to clearly understand some new physical
details about the formation and triggering mechanism of twisting jet. We
identify a pre-existing flux rope associated with a sinistral filament, which
was observed several days before the event. The confined eruption of the
filament within a null point topology, also known as an Eiffel tower (or
inverted-Y) magnetic field configuration results in the formation of a twisted
jet after the magnetic reconnection near a null point. The sign of helicity in
the jet is found to be the same as that of the sign of helicity in the
filament. Untwisting motion of the reconnected magnetic field lines gives rise
to the accelerating plasma along the jet axis. The event clearly shows the
twist injection from the pre-eruptive magnetic field to the jet.Comment: 14 pages, 12 figures, to appear in MNRA
Wire GEM detector
A wire GEM (WGEM) detector with a gas gap between meshes was constructed. The
detector provides the amplification 5x10E5 for the gas mixture of Ar +20% CO2
at atmospheric pressure. As compared with well-known GEM detectors produced by
perforation the plastic plate metalized on both sides the WGEM does not suffer
from breakdowns between its electrodes and the effect of accumulation of
charges on holes walls is absent. As a result the WGEM has high reliability and
stability.Comment: Presented at the RD51 Collaboration Meeting, CERN, November 2009,
submitted to the Prib. Tech. Expe
RETGEM with polyvinylchloride (PVC) electrodes
This paper presents a new design of the RETGEM (Resistive Electrode Thick
GEM) based on electrodes made of a polyvinylchloride material (PVC). Our device
can operate with gains of 10E5 as a conventional TGEM at low counting rates and
as RPC in the case of high counting rates without of the transit to the violent
sparks. The distinct feature of present RETGEM is the absent of the metal
coating and lithographic technology for manufacturing of the protective
dielectric rms. The electrodes from PVC permit to do the holes by a simple
drilling machine. Detectors on a RETGEM basis could be useful in many fields of
an application requiring a more cheap manufacturing and safe operation, for
example, in a large neutrino experiments, in TPC, RICH systems.Comment: Presented at the RD51 Collaboration Meeting, CERN, November 200
Simulation of three-dimensional micromagnetic structures in magnetically uniaxial films with in-plane anisotropy: Static structures
The possible types of transition structures that can arise between the regions of vortex asymmetric domain walls that exist in magnetically uniaxial permalloy films with in-plane anisotropy have been studied by the method of three-dimensional computer simulation of the magnetization behavior. It has been established that, along with the previously found structures of vertical Bloch lines (VBLs), other types of structures can exist, namely, singular (Bloch) points and clusters that consist of VBLs and Bloch points. Spatial configurations and topological characteristics of transition structures have been calculated numerically. © 2013 Pleiades Publishing, Ltd
Transition micromagnetic structures in asymmetric vortexlike domain walls (Static solutions and dynamic reconstructions)
The possible types of transition structures with a three-dimensional magnetization distribution over regions in the vortex asymmetric domain walls that exist in magnetically uniaxial soft magnetic films with in-plane anisotropy are studied by computer simulation in terms of a micromagnetic approach. It is shown that the possible structure types include both the type of vertical Bloch lines that was discussed earlier in other works and new types, namely, singular (Bloch) points and clusters consisting of vertical Bloch lines and Bloch points. The spatial configurations of the transition structures are calculated and their topological properties are found. The numerical simulation of the dynamics of closely spaced substructure regions reveals various scenarios of their interaction, including annihilation accompanied by energy release and the excitation of nonlinear waves. © 2013 Pleiades Publishing, Ltd
Simulation of three-dimensional micromagnetic structures in magnetically uniaxial films with in-plane anisotropy. Dynamics and structural reconstructions
Transition processes in nonequilibrium micromagnetic structures that represent regions of various types of asymmetrical vortex domain walls with closely spaced transition structural elements, including vertical Bloch lines (VBLs), singular points, and clusters consisting of VBLs and singular points, have been studied by the method of three-dimensional numerical simulation of the magnetization behavior. The realization of various scenarios of dynamic behavior, including the annihilation of transition elements accompanied by the liberation of energy and the initiation of wave processes, has been shown to be possible. The simulation was performed for the case of magnetically uniaxial ferromagnetic films with an easy axis parallel to their surface with exact allowance for the inhomogeneous exchange, magnetoanisotropic, and magnetostatic interactions. © 2013 Pleiades Publishing, Ltd
Two-dimensional micromagnetic simulation of domain structures in films with combined anisotropy
The transformation of the domain structure of micrometer-thick films with variations in the induced uniaxial anisotropy constant with the easy magnetization axis perpendicular to the film surface has been investigated using numerical micromagnetic simulation in the framework of a two-dimensional model of the magnetization distribution. The case where the tetra-axial crystallographic anisotropy exists in the film with uniaxial magnetic anisotropy has been considered. The transformation of the open domain structure into the structure with a magnetic flux closed inside the sample has been investigated in detail, and new types of 109-degree and 90-degree vortex-like domain walls and periodic domain structures have been obtained. © 2013 Pleiades Publishing, Ltd
Free Vibrations and Buckling of a Thin Cylindrical Shell of Variable Thickness with Curvelinear Edge
Low-frequency vibrations and buckling under an uniform external lateral pressure of a thin cylindrical shell of variable thickness with curvelinear edge are analyzed. The asymptotic and finite element methods are used to get the vibration frequencies and critical loads. The vibration and buckling modes are also presented. The comparison of numerical and asymptotic results is performed
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