Variation of energetic particle precipitation with local magnetic time

The detailed study of the precipitation of magnetospheric particles into the atmosphere is complicated by the rather complex spatial configuration of the precipitation region and its variability with geomagnetic activity. In this paper we will introduce polar oval coordinates and apply them to POES observations of 30 keV to 2.5 MeV electrons and comparable protons to illustrate the dependence of particle precipitation on local time and geomagnetic activity. These coordinates also allow an easy separation of the spatial precipitation patterns of solar and magnetospheric particles. The results indicate that (a) the spatial precipitation pattern of energetic magnetospheric electrons basically follows the pattern of the field parallel Birkeland currents up to MeV energies and (b) at least in the mesosphere the influence of magnetospheric electrons is comparable to the one of solar electrons. Implications for modeling of atmospheric chemistry will be sketched.     

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。     

新的多重网格法求解离心压气机内部流场

受英国剑桥大学 Denton教授对叶轮机械数值计算的启发, 本文提出了一种新的多重网格法, 并将之与显式时间推进法、有限体积差分格式、粘性体积力法配合使用来求解离心压气机内部流场。数值计算表明, 作者多重网格法的计算结果与试验结果吻合很好, 同时该多重网格法的收敛速度比不用多重网格法加快了将近两倍, 也比 Denton多重网格法的收敛速度加快了将近 1倍。      

卫星强磁场干扰分析

文章对IGSO/MEO卫星采用的400A·m~2的磁力矩器周围的磁场分布进行了计算分析,计算表明距400A·m~2磁力矩器头部10cm处,磁场达到6．9×10~(-3)T。同时对部组件在磁场较强的环境中可能受到的影响进行了理论分析,并利用螺线管产生的磁场对星用DC/DC模块进行了测试。测试表明,部件的磁性变化只与其所处磁场环境有关,而与时间无关。同时,变化的磁场会对部件的内阻产生一定的影响,引起输入电流的变化,该变化会对部件的寿命带来一定的影响。     

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。