轴向流对Z箍缩等离子体稳定性的影响

利用理想磁流体力学(MHD)模型对有轴向流参与的Z箍缩等离子体不稳定性进行了分析.对可压缩平板等离子体模型的色散关系进行了推导，讨论了三种不同等离子体状态下的不稳定性增长率.结果显示，等离子体的可压缩性对磁瑞利-泰勒/开尔文-亥姆霍兹(MRT/KH)杂化不稳定性有抑制作用，改善了轴向剪切流对长波长扰动的影响.分析了不同轴向流速度分布对系统稳定性的影响.结果表明，对于峰值相同的不同轴向流，其对不稳定性的抑制效果只依赖于扰动集中区域内速度剪切的大小，与其他位置的速度剪切无关. 关键词： Z箍缩 磁瑞利-泰勒不稳定性 轴向剪切流 MHD方程     

轴向剪切流对Z箍缩等离子体瑞利-泰勒不稳定性的抑制

利用理想磁流体力学模型对有轴向剪切流的Z箍缩等离子体不稳定性进行了分析。给出了可压缩模型的色散关系,分别对可压缩及不可压缩模型中轴向剪切流对Z箍缩等离子体瑞利-泰勒不稳定性的抑制作用进行了比较,讨论了可压缩性对含有轴向剪切流系统不稳定性的影响。结果表明,可压缩性能够减缓瑞利-泰勒P凯尔文-亥姆霍兹(RTPKH)模扰动的增长,因而使得轴向剪切流对系统不稳定性的抑制作用表现得更为突出。计算结果还说明,在RT不稳定性线性增长阶段,等离子体温度较低,使用可压缩模型能够更真实地描述系统的状态。     

等离子体轴向运动对撕裂模不稳定性影响研究

从电阻磁流体模型出发,详细推导了柱形位形下低β等离子体中包括等离子体宏观轴向运动效应的电阻性撕裂模线性不稳定性理论。数值研究发现：等离子体轴向运动速度本身对撕裂模具有明显的稳定作用,而轴向运动速度剪切的作用并不明显。分析表明：轴向运动通过改变扰动势函数和磁通函数之间的相位差(偏离π/2)来降低撕裂模增长率,同时产生一个较低的撕裂模频率。     

等离子体放电柱磁螺旋不稳定性的线性理论

在静电磁流体方程基础上,提出了柱状放电电弧等离子体磁螺旋不稳定性的一种新的线性分析方法.通过数量级分析得到的简化扰动能量方程研究了外轴向磁场中阻抗粘滞m=1慢模,解析地给出了全部解和不稳定性增长率.并讨论了外加轴向磁场、弧电流和弧柱半径与外管壁半径相对大小等对电弧不稳定性的影响 关键词：     

有限拉莫尔半径和剪切轴向流组合稳定瑞利-泰勒不稳定性

本文参照不可压缩粘滞磁流体动力学方程，考查粘滞对环形等离子体内爆瑞利一泰勒（RT）不稳定性的影响。这里，粘滞效应按文献是指有限拉莫尔半径，用有限拉莫尔半径代替通常的平均自由程。换言之，把有限拉莫尔半径项看成有效粘滞项。即，在等离子体动量方程中称为同旋粘滞项。由于引入了速度剪切，开耳芬．亥姆霍兹不稳定性也包含其中。结果表明，在Z箍缩内爆中，有限拉莫尔半径对磁瑞利-泰勒不稳定性起强稳定作用，而且剪切轴向流和有限拉莫尔半径的组合效应能够极大减小瑞利-泰勒不稳定性。     

旋转圆柱等离子体中撕裂模和Kelvin-Helmholtz不稳定性的激发特性

采用约化的磁流体力学模型,数值研究了柱位形等离子体中q剖面和极向旋转剖面对q=1撕裂模不稳定性和Kelvin-Helmholtz(K-H)不稳定性的影响.随着旋转强度的增加,m/n=1/1模被逐渐抑制,而高阶谐波模式(如m/n=2/2,m/n=3/3等)会经历四个区间:撕裂模失稳区间、撕裂模致稳区间、稳定窗口区间和K-H不稳定性激发区间.更进一步,我们发现,m/n=1/1模的增长率随旋转强度的改变与剪切层所处位置有关,并且剪切层分布在有理面内外的结果基本一致;然而高阶谐波模式却没有此类现象.另外,有理面处磁剪切越小,撕裂模越容易被剪切流抑制,并且越容易激发K-H不稳定性.     

负磁剪切等离子体中离子温度梯度驱动不稳定性分析

采用打靶法,数值求解了在负磁剪切托卡马克等离子体中离子温度梯度驱动的复本征模方程.数值计算表明,环向旋转剪切流可以整体上改变剪切板η_i不稳定性.在等离子体极小q磁面附近的芯部区域,环向剪切流有稳定η_i模的作用.     

电弧螺旋不稳定性理论的简化分析和数值研究

在静电磁流体方程基础上提出了柱状放电电弧等离子体的磁螺旋不稳定性的一种新的线性分析方法。通过数量级分析得到了简化扰动能量方程。数值研究了外加轴向磁场、输入功率和弧柱半径外管壁半径相对大小等对电弧不稳定性的影响。     

电弧螺旋不稳定性理论的简化分析和数值研究

在静电磁流体方程基础上提出了柱状放电弧等离子体的磁螺旋不稳定性的一种新的线性分析方法。通过数量级分析得到了简化扰动能量方程。数值研究了外加轴向磁场、输入功率和弧柱半径外管壁半径相对大小等对电弧不稳定性的影响。     

等离子射流的磁流不稳定性

1.当无限均匀等离子射流的速度,超过在完全电离的背景等离子体中的折合阿尔芬波速时,射流相对于微小磁流扰动,将是不稳定的。这类不稳定性,与在日地关系问题中所观测到的某些现象的解释有关。在许多情况下,由于存在足够数量的中性粒子(如在电离层或大部分实验装置中),往往必须考虑它们的影响,因此,本文将讨论在部分电离的背景等离子体中,等离子射流的磁流不稳定性问题。所得结果表明:在强耦合与弱耦合下,但ωγ_i时,在部分电离的背景等离子体中,不稳定性条件与在完全电离介质中的情况相比,有较显著的差别。     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

On the predictability of the positions of the convergence zones in the ocean

The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.     

On the calculation of the bremsstrahlung in the region of the plasma frequency

On the basis of the classical theory of radiation produced in incomplete Coulomb interaction, a formula is derived for the coefficient of the bremsstrahlung of fully ionized plasma. In the region of rectilinear approximation a comparison is made with the results of the quantum formula derived from the Born approximation. Furthermore, the influence of dispersion upon the emission coefficient is taken into account; some relations for the region of dispersion are given.     

Dependence of the Intensity of the Spectral Lines and the Composition of the Sample and the Plasma Parameters of the Unipolar Arc

The investigation was made of the dependence of the intensity of Tl, Ga, Mo, Mg, Mn, Sn, Bi, Ni, Zn, Pt and Au spectral lines and the plasma parameters (temperature T, electron concentration n_e, degree of 6 ionnization α) from concentration of lithium additive.     

Extracting the wavefunction of the LSP at the LHC

We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables - including some introduced here for the first time - we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments.     

Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.     

On the Question of the Source of the Apokamp

Technical Physics - The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage...