Cluster Observation of Eelectrostatic Solitary Waves around Magnetic Null Point in Thin Current Sheet

Electrostatic solitary waves （ESWs） are observed in the vicinity of the magnetic null of the widely studied magnetic reconnection taking place at the near-earth tail when current sheet becomes dramatic thinning during substorm time on 1 October 2001. We use the Imada method for the 2-D reconnection model and study the characteristics of ESWs near the X-line region and the magnetic null points. The result shows that the amplitude of the observed ESWs in the vicinity of X-line region ranges from 0.1mV/m to 5mV/m, and the amplitude is larger near the magnetic null points. The generation mechanism and the role of ESWs associated with magnetic reconnection are also discussed.     

Properties of Field Aligned Current in Plasma Sheet Boundary Layers in Magnetotail: Cluster Observation

Field aligned current （FAC） distribution in the plasma sheet boundary layers （PSBLs） in the magnetotail is studied statistically by analysing magnetic field data from the Cluster 4-point measurements. The results show that the FAC distribution on the dusk side is not the same as that on the dawn side in the magnetotail. On the each side earthward and tailward, FA C occurrences are different; occurrence and average current density of FA Cs in the northern hemisphere are different from those in the southern hemisphere. This implies that the FACs have dusk-dawn side asymmetry, polarity asymmetry and inter hemisphere difference in the magnetotail. The present results give a good observation evidence for study on the FAC mechanism.     

Anomalous Electric Fields Inside a Dense Plasma of a Current Sheet

For the first time there have been analyzed profiles of electric-field-sensitive n_a spectral lines of the Li-like impurity ions CIV, NV, OVI emitted by a hot dense plasma of a plane current sheet. Theoretical profiles of these lines have been calculated with an allowance for Anomalous Electric Fields (AEF). By comparing the experimental and theoretical profiles of the lines it has been established for the first time that in the plane current sheet there were developed AEF of rms strengths F₀ ≈ (100–120) kV/cm in the time interval from τ = ?0.2 μs to τ = 0 (the time τ was counted from the instant of the maximum intensity of the spectral line OVI 5291 Å). These results have been backed up by a similar analysis of the experimental profiles of the spectral line HeII 4686 Å of the primary gas of the discharge. The AEF reached these strengths at the same instant of time, τ = ?0.2 μs, when electron and ion temperatures reached their maxima: T_e ? 100 eV, T_i ≈ 300 eV. The instant τ = ?0.2 μs corresponds to a transition from the metastable stage to the explosive phase of the current sheet evolution. At this time the ratio of the AEF energy density to the thermal energy density of the plasma was § ≡ F²₀/[8π/N_eT_e + N_iT_i)] ≈ 10^?3, which exceeded a similar ratio for the thermal wave field by three orders of magnitude.     

Current Distribution in a Gyrotropic Microstrip Structure when Excited by a Plane Electromagnetic Wave

The problem of the distribution of the surface current density in a gyrotropic microstrip structure representing an infinitely thin ideally conducting strip arranged on a substrate of a chiral metamaterial metallized from one side and excited by a plane wave is reduced to a one-dimensional singular integral equation with a Cauchy singularity. The complex current distributions along the strip conductor are presented for different types of substrate and the wave-incidence angles.     

具有尺寸限制的点接触结构自旋极化电流驱动下磁涡旋的稳态振荡

选取具有尺寸限制的点接触结构作为研究对象,采用Thiele方程对模型中磁涡旋在自旋极化电流作用下的动力学行为进行计算.计算表明磁涡旋可以在一定的电流密度范围内稳定旋转,该稳定旋转可以存在的电流密度范围与点接触区的大小和纳米点的尺寸有关.当磁涡旋核作稳态旋转时,其所处的轨道半径以及旋转频率都随电流密度的增加而增加,旋转频率可调节的范围随点接触尺寸的增加快速减小.     

TM光子在受抑全内反射结构中的隧穿时间

用电磁场的能量转移速度定义了TM光子在受抑全内反射结构中的隧穿时间，对所得结果进行了分析和讨论，并把这个结果与TE光子隧穿的时间进行了比较。     

Nonlinear Evolution of Lower-Hybrid Drift Instability in Harris Current Sheet

We perform 2.5-dimensional particle-in-cell simulations to investigate the nonlinear evolution of the lower hybrid drift instability (LHDI) in Harris current sheet. Due to the drift motion of electrons in the electric field of the excited low hybrid drift (LHD) waves, the electrons accumulate at the outer layer, and therefore there is net positive charge at the inner edge of the current sheet. This redistribution of charge can create an electrostatic field along the z direction, which then modifies the motions of the electrons along the y direction by E×B drift. This effect strongly changes the structure of the current sheet.     

Parameters of the Plasma Sheet Generated by a Sheet Beam in the Range of Forvacuum Pressures

Results of experimental investigations into the spatial distribution of the parameters of the plasma (electron concentration and temperature) generated by a sheet beam with energy up to 2 keV in argon at pressures from 6 to 9 Pa are presented. The electron beam was produced by a source with a plasma cathode specially designed for emission of beams in the range of forvacuum pressures. It is demonstrated that the character of distribution of the plasma parameters is caused by the corresponding distribution of the electron current density over the beam cross section, and the plasma parameters themselves also noticeably depend on the gas pressure and the magnetic field. A model of ionization processes that provides satisfactory agreement between the calculated and experimental dependences is suggested.     

Autoinjection of Single-Pulse Priming Radiation in a Laser with a Bifurcated Anisotropic Resonator

The optical schemes of lasers with autoinjection of priming radiation in a bifurcated anisotropic resonator are described that make it possible to increase the efficiency of the formation of highly coherent giant pulses by raising the priming radiation intensity level. The parameters of radiation of that kind of ruby lasers have been experimentally studied with Q-switching of a low Q resonator by a bleaching filter and electrooptical switching of the generation channel into the resonator with a higher Q and/or the gain coefficient of an active element, and/or the active material space factor of the resonator.     

双中子集团结构研究进展

回顾了晕核发现以来双中子集团结构的研究进展,分析了可能的发展方向。系统的理论研究表明, 在原子核的表面和低密度核物质中, 空间紧密关联的2n集团的出现是一个普遍的现象。 但在较重原子核表面出现2n集团的机制与核物质或轻晕核中的机制很不一样, 前者是由有限核的平均场造成的尺度效应（size effect）,而后者主要是由低密度下对相互作用（或对能隙）的增强造成的。另外,在轻晕核或有限核表面,2n集团的均方根半径与它们到核芯的距离（或背景密度）有关,最小值普遍可以达到2～3 fm,然而在核物质中2n集团最小只能到～5 fm。 实验方面,在重靶上的库仑激发强度, 能够比较准确地给出2n系统到核芯的平均距离。 但到目前为止尚没有有效的实验方法给出基态中两个中子之间的间距, 主要原因是中子发射过程中末态相互作用（共振态或虚粒子态）造成的两步过程的干扰, 这个问题在库仑激发破碎（重靶）或核作用破碎（轻靶）中都出现。“拖出”反应和敲出核芯反应是下一步可以考虑的路径。 双中子的关联测量通常效率比较低,尤其是需要有效排除中子串扰(CT)事件。为此, 需要发展特殊设计的中子关联测量装置, 在提高探测效率的同时,能够通过运动学关系以及其他方法有效排除中子CT信号。 在数据处理阶段,通过反复迭代给出的双中子关联函数, 经验证明是比较有效的关联状态表达方式, 从中可以直接提取出双中子分布均方根半径。 This article outlines the progress in the study of the di neutron structure in various systems. Systematic theoretical investigations reveal that di neutron structure is a general phenomenon appeared at nucleus surface and in low density nuclear matter. But the underline mechanism of forming di neutron clusters at the surface of heavier nuclei is quite different to that for light halo nuclei or at the low density nuclear matter, with the former being basically due to the so called “size effect” and the latter due to the enhanced pairing interaction. It is also realized that the RMS radii of the di neutron cluster at the surface of light halo nuclei or heavier finite nuclei varies with the distance from the center of nuclei (or background density) and may attain a minimum of about 2～3 fm, whereas that in the low density nuclear matter may only attain about 5 fm. From experimental side, Coulomb excitation caused by heavy targets provides a good way to extract the mean distance from the center of the neutron pair to the center of nucleus. But up to now it is still difficult to experimentally determine the distance between the two valence neutrons, due primarily to the final state interactions which lead to two step emission of neutrons via resonances or virtual intermediate states. This problem happens in both Coulomb and nuclear breakup processes. Possible ways to avoid this problem might come from experiments based on “towing mode” or core knockout reactions. Detection of two neutrons in coincidence often suffers from low efficiencies and the need to reject the cross talk events. Therefore it is important to develop specially designed multi neutron detection array to achieve high efficiency as well as good cross talk rejection performance using kinematics conditions. For data analysis, it was found that two neutron correlation function generated by iteration method is a good expression of the correlation situation, from which the RMS radii of the two neutron distribution may be deduced.     

Anomalous Scaling of the Ion Beam Energy in the Current Sheet

JETP Letters - The scaling of the energy of ion beams (beamlets) WN ∼ NA in the N resonant regions of the current sheet in data from the SC-1 and SC-4 CLUSTER satellites has been analyzed....     

Electron Transport in Graphene-Based Double-Barrier Structure under a Time Periodic Field

The transport property of electron through graphene-based double-barrier under a time periodic field is investigated. We study the influence of the system parameters and external field strength on the transmission probability. The results show that transmission exhibits various kinds of behavior with the change of parameters due to its angular anisotropy. One could control the values of transmission and conductivity as well as their distribution in each
band by tuning the parameters.     

Sheet sticking caused by charge flow in a buried conducting layer

Electrostatic charge causes sheets to misfeed from the input stacks in inkjet and laser printers. Conductive layers within sheets that suppress discharges and reduce particulate contamination also aggravate sheet sticking. The surface potential of sheet media is a direct measure of the charge in the buried conducting layer. Our experiments find that the times characterizing the voltage transients range from 10 to 1000 s for conductive layers with sheet resistivities in the range from 10⁺⁹ to 10⁺¹¹ Ω/□. Our models predict that charge flowing in the conducting layer increases the electrostatic sticking force. Model predictions are in agreement with our experimental measurements.     

Poisson Structures Compatible with the Cluster Algebra Structure in Grassmannians

The present paper is a first step toward establishing connections between solutions of the classical Yang–Baxter equations and cluster algebras. We describe all Poisson brackets compatible with the natural cluster algebra structure in the open Schubert cell of the Grassmannian G _k (n) and show that any such bracket endows G _k (n) with a structure of a Poisson homogeneous space with respect to the natural action of SL _n equipped with an R-matrix Poisson–Lie structure. The corresponding R-matrices belong to the simplest class in the Belavin–Drinfeld classification. Moreover, every compatible Poisson structure can be obtained this way.     

Cluster Structure of Optimal Solutions in Bipartitioning of Small Worlds

Using simulated annealing, we examine a bipartitioning of small worlds obtained by adding a fraction of randomly chosen links to a one-dimensional chain or a square lattice. Models defined on small worlds typically exhibit a mean-field behavior, regardless of the underlying lattice. Our work demonstrates that the bipartitioning of small worlds does depend on the underlying lattice. Simulations show that for one-dimensional small worlds, optimal partitions are finite size clusters for any fraction of additional links. In the two-dimensional case, we observe two regimes: when the fraction of additional links is sufficiently small, the optimal partitions have a stripe-like shape, which is lost for a larger number of additional links as optimal partitions become disordered. Some arguments, which interpret additional links as thermal excitations and refer to the thermodynamics of Ising models, suggest a qualitative explanation of such a behavior. The histogram of overlaps suggests that a replica symmetry is broken in a one-dimensional small world. In the two-dimensional case, the replica symmetry seems to hold, but with some additional degeneracy of stripe-like partitions.     

Spectral Line HeII 6560 Å as a Sensor of the Electron Concentration in a Dense Plasma of a Current Sheet

Stark broadening of the spectral line HeII 6560 Å by plasma was studied. The profiles of the line HeII 6560 Å were calculated for different values of the electron concentration N_e. We used the quasi‐static approximation to account for the perturbing ions and the impact approximation to describe the perturbing electrons. The electron concentration N_e in the central region of a current sheet plasma was deduced by comparing the experimentally obtained profiles of the line HeII 6560 Å with the set of the theoretically calculated profiles of this line.     

Time Jitters in Multiple-Core Fiber of Ring Structure

Property of soliton propagation is analyzed by using self-companying operator method in multiple-core fiber of ring structure. The results show that the time jitters of soliton transmission in every core relate to the relative amplitude among the input solitons in the multiple-core fiber.