Advances in space research nonlinear dependence of Dst and AE indices on the electric field of magnetic clouds

Using the Dst and AE geomagnetic index values and parameters of interplanetary magnetic field and solar wind we have examined the geoeffectiveness of transient ejections in the solar wind, namely, magnetic clouds and high-speed streams. It is found that for magnetic clouds the dependences of indices on the solar wind electric field are nonlinear of different kind. In contrast to magnetic clouds, the dependence of Dst and AE geomagnetic index values on the solar wind electric field agrees closely with the linear one for high-speed streams. We suggest approximating formulas to describe dependences obtained taking into account the relation of the electric field transpolar potential to the electric field and dynamic pressure of the solar wind. We suppose that the interplanetary magnetic field fluctuations also contribute to these dependences.     

超高速碰撞数值模拟的工程算法模型

提出了双层板防护结构的超高速碰撞数值模拟的工程算法模型，采取理论分析、经验公式和数值模拟相结合的研究方法来模拟碎片云的产生，以及碎片云对结构的破毁过程。本模型中，碎片云的产生采用理论分析和经验公式得到，结构响应采用有限元动力学软件Dyna3D进行计算。数值模拟结果与文献中给出的破坏效果基本一致，说明提出的工程算法是可行的，模拟得到的结果能定性的描述相应的超高速碰撞的现象，得到基本正确的结果。     

两种物态方程在超高速碰撞数值模拟中的比较

材料在超高速碰撞下将发生熔化甚至气化相变。为反映超高速碰撞中材料相变带来的影响,文章采用GRAY三相物态方程与Tillotson物态方程,对超高速碰撞进行数值模拟对比研究。研究表明:当碰撞速度在3 km/s以下时,除了靶板穿孔直径外,两种物态方程所给出的碎片云的结果基本一致;但当碰撞速度在3 km/s以上时,两种物态方程给出的数值模拟结果有较大差异,这说明在超高速碰撞中相变的产生对碎片云形状参数有较大影响。     

Evolution of coronal mass ejection/shock system in interplanetary space

The evolution of coronal mass ejection/shock system is investigated by numerically solving the usual set of two-dimensional single-fluid polytropic magnetohydrodynamic equations from 1 R_s to 1 AU in the meridian plane. The simulation result reveals that the coronal mass ejection/shock system formed near the sun evolves into the magnetic cloud/shock system near the earth’s orbit through the following three phases: the initial formation, the dominant latitudinal expansion and the similar expansion.     

On the dynamics of the heliosphere on intermediate and long time-scales

A time-dependent, three-dimensional model of the dynamics of the heliosphere as a result of solar activity and a time-varying local interstellar medium is presented. The model is based on a recent version of the well known ZEUS code and employs parallel processing. It includes the solar and interstellar plasma components as well as neutral atoms, and contains the heliospheric magnetic field in a kinematic fashion. We study the dynamics of the heliosphere due to solar activity on periods of months to years up to the so-called Schwabe (11-year) cycle as well as due to time variations of the local interstellar medium, all of which have drawn increasing attention during recent years, as the significance of their direct or indirect effect on the Earth and its environment is under lively debate.     

一种翻滚火箭箭体的运动参数估计方法

针对处于自由翻滚运动状态的火箭箭体,其呈回转体结构,运动参数估计难的问题,提出了一种翻滚火箭箭体的运动参数估计方法。采用激光成像雷达获取目标的三维点云数据,通过点云法向量估计和随机采样一致性算法计算得到自旋轴;然后结合序列各帧的自旋轴估计结果,采用最小二乘法求解得到翻滚火箭箭体的翻滚轴;进而利用相邻两帧的自旋轴和翻滚轴估计结果求解得到章动角和空间章动角速率。基于仿真数据对方法进行了实验及分析,结果表明该方法能够有效地估计自由翻滚状态的火箭箭体的翻滚轴、章动角和空间章动角速率。     

Model-independent large-scale magnetohydrodynamic quantities in magnetic clouds

Magnetic clouds are the interplanetary manifestation of coronal mass ejections, which are transient expulsions of major quantities of magnetized plasma, from the Sun toward the heliosphere. The magnetic flux and helicity are two key physical magnitudes to track solar structures from the photosphere-corona to the interplanetary medium. To determine the content of flux and helicity in magnetic clouds, we have to know their 3D structure. However, since spacecrafts register data along a unique direction, several aspects of their global configuration cannot be observed. We present a method to estimate the magnetic flux and the magnetic helicity per unit length in magnetic clouds, directly from in situ magnetic observations, assuming only a cylindrical symmetry for the magnetic field configuration in the observed cross-section of the cloud. We select a set of 20 magnetic clouds observed by the spacecraft Wind and estimate their magnetic flux and their helicity per unit length. We compare the results obtained from our direct method with those obtained under the assumption of a helical linear force-free field. This direct method improves previous estimations of helicity in clouds.     

基于隶属云发生器的智能控制

阐述一种利用隶属云发生器实现智能控制的方法。其控制策略是通过语言值构成规则,从而形成一种直观推理方法。它不要求给出被控对象精确的数学模型,仅仅依据人的经验、感觉和逻辑判断,将人用语言值定性表达的控制经验,通过语言原子和云模型转换到语言控制规则器中,就能解决非线性问题和不确定性问题。基于此理论控制倒立摆获得比较好的效果,结果表明,该方法对被控对象的状态和参数变化具有较强的鲁棒性。     

海量数据三角网格生成算法

对海量数据散乱密集难以自动得到邻近点间正确拓扑连接关系的问题,给出了一种用于海量数据的基于增量网格扩展的三角剖分方法.该方法以k阶最近邻域算法快速搜寻边界点的最近邻域,以增量算法的边界环为基础向外生成三角形,实现点云数据点之间合理的三角剖分网格建立.对最佳点的选择提出了3种需遵循的新准则,并根据最佳点的位置不同,详细给出了3种网格拓扑操作来构建新三角网格,可以准确的进行三角剖分.车身曲面测量点云的应用实例表明,该算法可以高效,稳定地直接构建出车身曲面三角网格.      

Aerosol Effects on Clouds and Climate

Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei, they may inhibit freezing and they could have an influence on the hydrological cycle. While the cloud albedo enhancement (Twomey effect) of warm clouds received most attention so far and traditionally is the only indirect aerosol forcing considered in transient climate simulations, here I discuss the multitude of effects.