New index of long-term variations of galactic cosmic ray intensity

We find that the soft rigidity spectrum of the Galactic Cosmic Ray (GCR) intensity variations for the maximum epoch and the hard rigidity spectrum for the minimum epoch calculated based on the neutron monitors experimental data (1960–2002) are related with the various dependence of the diffusion coefficient on the GCR particle’s rigidity for different epoch of solar activity. This dependence is stronger in the maximum epoch than in the minimum epoch of solar activity, and is provided by the essential temporal rearrangements of the structure of the Interplanetary Magnetic Field (IMF) turbulence from the maxima to minima epoch of solar activity. We also show that the rigidity spectrum of GCR intensity variations is harder for the effective rigidities ∼(10–15) GV (by neutron monitors data), than for the effective rigidities ∼(25–30) GV (by neutron monitors and muon telescopes data). A general scenario of GCR modulation versus solar activity is settled on the essential temporal rearrangements of the structure of the IMF turbulence. Therefore, the temporal changes of the power law rigidity spectrum exponent can be considered as a vital (new) index to explain the 11-year variations of the GCR intensity. We assume that ∼(70–80)% of the changes of the amplitudes of the 11-year variations of GCR intensity is related with the changes of the IMF turbulence versus solar activity.     

Whistler waves in plasmas with time-varying magnetic field: Laboratory investigation

Modulation of whistler waves in a plasma with time-dependant magnetic field perturbations was investigated experimentally. The experiments were performed on large “Krot” device, which was specially designed to study space plasma physics phenomena. It is shown that magnetic field variations on the wave propagation path can lead to splitting of initially continuous whistler wave into the sequence of bursts, whose repetition rate corresponds to magnetic field perturbation period. The frequency inside each burst is changing from its front edge to the back edge. Relative shift of the wave frequency can be as large as the relative magnetic disturbance. Distortion of whistler wave frequency spectrum after its passing through magnetically disturbed areas can be used as a diagnostics for low-frequency magnetic field variations. The applicability of our laboratory results to space plasma is discussed.     

A question raised from the observation of dynamic cusp formation: When and where does particle acceleration occur?

We present observations of a C9.4 flare on 2002 June 2 in EUV (TRACE) and X-rays (RHESSI). The multiwavelength data reveal: (1) the involvement of a quadrupole magnetic configuration; (2) loop expansion and ribbon motion in the pre-impulsive phase; (3) gradual formation of a new compact loop with a long cusp at the top during the impulsive phase of the flare; (4) appearance of a large, twisted loop above the cusp expanding outward immediately after the hard X-ray peak; and (5) X-ray emission observed only from the new compact loop and the cusp. In particular, the gradual formation of an EUV cusp feature is very clear. The observations also reveal the timing of the cusp formation and particle acceleration: most of the impulsive hard X-rays (>25 keV) were emitted before the cusp was seen. This suggests that fast reconnection occurred during the restructuring of the magnetic configuration, resulting in more efficient particle acceleration, while the reconnection slowed after the cusp was completely formed and the magnetic geometry was stabilized. This observation is consistent with the observations obtained with Yohkoh/Soft X-ray Telescope (SXT) that soft X-ray cusp structures only appear after the major impulsive energy release in solar flares. These observations have important implications for the modeling of magnetic reconnection and particle acceleration.     

磁空间群PC 63/mmc的C-G系数计算

在晶体拉曼散射的张量计算中，晶体磁空间群的C-G系数具有重要的作用。利用本征函数法计算了Pc63／mmc磁空间群第一布里渊区中的对称点A之间的C-G系数。     

电磁轴承支承的柔性转子在轴承失效后坠落过程中的瞬态响应

研究了主动电磁轴承支承的单盘柔性转子系统在磁轴承失效后转子坠落在带有固定间隙的滚动型备用轴承上的瞬态响应,分析了备用轴承的各种参数对瞬态响应的影响。结果发现系统出现了以自由落体-碰撞弹起-自由落体为特征的在间隙圆底部的摆动运动、以碰撞弹起-加速落体-碰撞弹起为特征的在整个间隙圆范围的碰撞型回转运动以及轴颈与备用轴承始终接触在一起的摩擦型回转运动等3种运动形式。碰撞型回转运动实际上是由碰撞过程中部分周向的摩碰引起,而摩擦型回转运动是由轴颈与备用轴承之间的全周干摩擦所致。碰撞型回转运动和反向摩擦型回转运动对备用轴承的影响最为严重。     

磁悬浮柔性转子系统变学习速率单神经元PID控制

磁悬浮轴承柔性转子系统的转速范围较大,固定的控制参数很难同时保证系统所需的低频和高频特性。本文在一般单神经元PID控制的基础上,将转速信号引入磁悬浮轴承数字控制器,在不同转速段选择不同的学习速率以调节控制参数得到合适的磁悬浮轴承的刚度和阻尼。试验结果表明,变学习速率单神经元自适应PID控制能够明显减小转子在各阶临界转速时的振幅,有助于磁悬浮轴承柔性转子系统的安全稳定运行。     

压力对Fe_（16）N_2结构和磁性的影响

用基于密度泛函理论的第一性原理方法,系统地研究了压力对Fe16N2体系结构和磁性的影响。结果表明仅仅离N位最远的Fe Ⅲ拥有一个约为2.84μB的大磁矩,而FeⅠ和Fe Ⅱ原子没有大磁矩产生。此外,还发现从0到47 GPa,总磁矩和单胞体积随着压力的增加单调减小,然而,在48 GPa的压力作用下,伴随着单胞体积的剧减,体系总磁矩消失。     

磁探仪应召搜潜建模与仿真

依据经典的磁探仪应召搜潜方法,以某型反潜巡逻机为背景,建立了反潜巡逻机利用磁探仪执行平行航线、扩展矩形和螺旋形搜潜模型.对3种方法的搜潜概率进行分析,仿真了相同潜艇运动模型条件下,潜艇初始位置散布、初始距离、潜艇经济航速和海洋环境磁噪声对搜潜概率的影响.实验结果表明:相同条件下,螺旋形搜潜效能最高;潜艇只进行航速机动时...     

冷原子导引囚禁磁场的计算及分析

为了研究冷原子在磁导引中的运动规律,设计优化导体结构、电流和偏置磁场,本文根据毕奥-萨伐尔定律计算理想化导体的常规数值解,并由Matlab和VC混合编程设计出导线磁场计算工具;根据麦克斯韦方程组选择Ansoft MaxweU计算宽导线、复杂结构导体、通交变电流等情况的有限元数值解.取宽度为100μm,高度为10μm的宽...     

温度对磁屏蔽霍尔推力器磁场构型的影响研究

霍尔推力器磁路设计主要通过常温静态磁场仿真得到,并实测推力器非工作状态常温磁场进行复核。大功率霍尔推力器将面临更为严峻的热问题,推力器工作时磁路系统受高温影响,因此在常温下仿真得到的磁场位形会因温度升高而产生偏移,不能反映推力器真实工作时的磁场情况。为研究霍尔推力器工作时热量对磁路系统的影响,通过热磁耦合仿真对10 kW磁屏蔽霍尔推力器的热态磁场分布进行研究,并对热态、常温仿真结果进行了对比,发现在阳极附近的径向磁感应强度B_r的差异比放电室出口更大。常温设计的磁屏蔽构型在热态时偏离磁屏蔽,磁场和壁面最大不符合度达到13%,通过陶瓷出口型面修正后重新获得磁屏蔽效果,使最大不符合度降低到4.8%以下。合理热设计有助于降低热载荷,热仿真得到磁路系统最高温度低于500℃,低于0.78倍的居里温度T_c磁性急剧转变点,不会出现磁性能急剧下降,但热量对磁屏蔽霍尔推力器磁场构型的影响是应该考虑的。