Estimation of the bias of the Minimum Variance technique in the determination of magnetic clouds global quantities and orientation

Magnetic clouds (MCs) are highly magnetized plasma structures that have a low proton temperature and a magnetic field vector that rotates when seen by a heliospheric observer. More than 25 years of observations of magnetic and plasma properties of MCs at 1 AU have provided significant knowledge of their magnetic structure. However, because in situ observations only give information along the trajectory of the spacecraft, their real 3D magnetic configuration remains still partially unknown. We generate a set of synthetic clouds, exploring the space of parameters that represents the possible orientations and minimum distances of the satellite trajectory to the cloud axis, p. The synthetic clouds have a local cylindrical symmetry and a linear force-free magnetic configuration. From the analysis of synthetic clouds, we quantify the errors introduced in the determination of the orientation/size (and, consequently, of the global magnetohydrodynamic quantities) by the Minimum Variance method when p is not zero.     

Ionospheric disturbances detected by MEXART

The radio telescope MEXART was developed to make observations of interplanetary scintillation (IPS) produced by large scale disturbances associated with solar events. In this work it is shown that on occasion there are disturbances in the ionosphere that are related with these events and which cannot only contaminate the IPS but actually be the main contribution to the observed oscillations. This was the case of the event of 15 December 2006 observed by MEXART, which presented clear scintillation. The total electron content (TEC) of the ionosphere above Mexico was calculated for the same period. It was found that the variations in TEC were associated with the scintillations detected by MEXART.     

Two-dimensional launch window method to search for launch opportunities of interplanetary missions

Accurate and highly efficient approaches to obtain mission opportunities are still the goals of mission planners of interplanetary explorations. The search for launch opportunities not only determines the specified launch window of the mission but also presents the performance requirements for the interplanetary probe and its launch vehicle. An effective method, namely the two-dimensional launch window method, is developed from a completely new perspective to determine all the launch opportunities of the mission in this research. For a fixed launch time, the method to determine all the time windows in the dimension of Time-of-Flight (TOF) is firstly proposed and these time windows represent all the launch opportunities for the given launch time. And then, the two-dimensional launch window method is proposed, which computes the time windows in both the launch time and TOF dimensions to achieve all launch opportunities of the mission. Numerical examples are provided to demonstrate the accuracy and high efficiency of the method. Compared with the widely-used pock-chop plot method, the proposed method reduces the computational time by two orders of magnitude for the same search precision, and thus is especially suitable for the cases involving rapid, high-precision, and/or large-scale searches for mission opportunities.     

Advance of interplanetary physics study in China: 2008—2010

Interplanetary physics study is an important ingredient in space weather research. Considerable progress this aspect has been achieved by the space physics community of China in recent years. This brief report summarizes the latest advances of the interplanetary physics research in China during the period of 2008--2010. This report includes solar corona and solar wind, interplanetary transients, energetic particles, MHD simulation, space plasma, and prediction methods for physical phenomena originating from both solar corona and interplanetary space.      

Energy dependence of the rigidity spectrum of Forbush decrease of galactic cosmic ray intensity

We show that rigidity spectrum of Forbush decrease (Fd) of galactic cosmic ray (GCR) intensity in September 9–23, 2005 clearly depends on energy. We calculated rigidity spectrum of the Fd based on the neutron monitors and Nagoya muon telescope channels’ data divided in three groups according to their cut off rigidities. We found that temporal changes of rigidity spectrum exponent γ are approximately similar for all cut off rigidity groups, but γ values are the larger the higher are cut off rigidities. We conclude that rigidity spectrum of Fd is hard for lower energy range and is soft for the higher energy range. We believe that an energy dependence of the power law rigidity spectrum of Fd is observed owing to the preferential convection–diffusion mechanism during Fd in September 9–23, 2005. It is a reflection of an influence of the temporal changes of the structure of the interplanetary magnetic field (IMF) turbulence in different range of frequency f during Fd. Particularly, a decisive role in formation of the character of the rigidity spectrum belongs to the changes of the exponent ν of the power spectral density (PSD) of the IMF turbulence (PSD ∝ f^−ν). The exponent ν is greater for high frequency region of the IMF turbulence (responsible for scattering of low rigidity particles of GCR), than for low frequency region of the IMF turbulence (being responsible for scattering of higher rigidity particles). Also, we challenge to estimate an existence of slab/2D structure of solar wind turbulence during the Fd in September 9–23, 2005 based on the distribution of average turbulence energy among the IMF’s components.     

Hierarchical approach for fast searching optimal launch opportunity in a wide range

Launch opportunity search is crucial for preliminary design of interplanetary trajectories. However, it is difficult to obtain the optimum solution efficiently when the range of search is wide. In this paper, a new fast search algorithm based on a modified hierarchical approach is proposed. At the top level, a simplified Pork-Chop diagram is plotted by sampling interpolation to delimit the candidate regions of the optimal solution. Each candidate region contains only one optimal solution, which fundamentally avoids the local optimal problem of genetic algorithms. At the bottom level, a hybrid optimization approach combining the genetic algorithm and the conjugate directions method is used to solve the accurate optimal solution of each candidate region and obtain the global optimal launch opportunity in the whole wide range of search. Simulation results show that the proposed hierarchical approach can quickly and robustly find the global optimal launch opportunity in a wide search space.     

行星际闪烁功率谱的Fresnel现象与太阳风速度

讨论了弱散射条件下行星际闪烁(IPS)功率谱的Fresnel现象。数值计算结果表明,无行星际扰动存在时,IPS功率谱的膝点频率仍是Fresnel频率,在日张角。ε≤35°的范围内,Fresnel振荡现象仍然存在,极小值所在频率与太阳风电子密度为一维结构薄屏近似的解析结果相差不大。行星际扰动存在时,功率谱的膝点频率并未改变,扰动区太阳风速度决定着Fresnel振荡出现的频率。      

行星际火箭和人造行星卫星的轨道设计问题

本文探讨行星际探测器和人造行星卫星的动力学模型,研究它们的运动轨道,给出飞行时间的近似式,并且从飞行时间和消耗能量二个方面对它们的轨道设计问题提出了一些新的看法.另外,文中还讨论了人造行星卫星的运动及其稳定条件.      

2004年12月13日IMF北向期间极区亚暴电离层电动力学特征

利用KRM地磁反演方法, 结合北半球中高纬度地磁台站数据, 研究了2004年12月13日行星际磁场北向期间发生的亚暴事件, 极区电离层电动力学参量(电流矢量、等效电流函数以及电势)的分布特征. 结果表明, 在该亚暴膨胀相起始后, 午夜之前西向电集流急剧增强, 且等效电流体系表现为夜侧双涡, 同时伴随夜侧增强的南向电场. 由于极弱的直接驱动过程, 卸载过程引起的电离层效应得到清楚显示. 卸载过程在膨胀相期间起绝对主导性作用. 同时, 夜侧电导率的增强是电集流区域电流急剧增强的主要原因.      

基于WWW的分布式计算

介绍了基于ＷＷＷ（Ｗｏｒｌｄ ｗｉｄｅ ｗｅｂ）服务,在Ｃｌｉｅｎｔ／Ｓｅｒｖｅｒ计算模式上采用分布对象技术和ＣＯＲＢＡ（Ｃｏｍｍｏｎ ｏｂｊｅｃｔ ｒｅｑｕｅｓｔ ｂｒｏｋｅｒ ａｒｃｈｉｔｅｃｔｕｒｅ）,并采用分布式计算语言Ｊａｖａ进行编程实现的企业分布式计算模型。Ｊａｖａ增强了ＷＷＷ的交互性,但它并不是一种解决Ｃ／Ｓ系统中互操作对象透明性的有效方法。当Ｊａｖａ和分布对象技术结合起来时,形成了