Corotating Interaction Regions at High Latitudes

Ulysses observed a stable strong CIR from early 1992 through 1994 during its first journey into the southern hemisphere. After the rapid latitude scan in early 1995, Ulysses observed a weaker CIR from early 1996 to mid-1997 in the northern hemisphere as it traveled back to the ecliptic at the orbit of Jupiter. These two CIRs are the observational basis of the investigation into the latitudinal structure of CIRs. The first CIR was caused by an extension of the northern coronal hole into the southern hemisphere during declining solar activity, whereas the second CIR near solar minimum activity was caused by small warps in the streamer belt. The latitudinal structure is described through the presentation of three 26-day periods during the southern CIR. The first at ∼24°S shows the full plasma interaction region including fast and slow wind streams, the compressed shocked flows with embedded stream interface and heliospheric current sheet (HCS), and the forward and reverse shocks with associated accelerated ions and electrons. The second at 40°S exhibits only the reverse shock, accelerated particles, and the 26-day modulation of cosmic rays. The third at 60°S shows only the accelerated particles and modulated cosmic rays. The possible mechanisms for the access of the accelerated particles and the CIR-modulated cosmic rays to high latitudes above the plasma interaction region are presented. They include direct magnetic field connection across latitude due to stochastic field line weaving or to systematic weaving caused by solar differential rotation combined with non-radial expansion of the fast wind. Another possible mechanism is particle diffusion across the average magnetic field, which includes stochastic field line weaving. A constraint on connection to a distant portion of the CIR is energy loss in the solar wind, which is substantial for the relatively slow-moving accelerated ions. Finally, the weaker northern CIR is compared with the southern CIR. It is weak because the inclination of the streamer belt and HCS decreased as Ulysses traveled to lower latitudes so that the spacecraft remained at about the maximum latitudinal extent of the HCS. This revised version was published online in August 2006 with corrections to the Cover Date.     

反压作用下隔离段性能估算方法研究

在前期隔离段研究结果基础上,对不同来流马赫数及不同反压下等直隔离段的出口温度、压力和马赫数进行了分析。通过大量拟合,得到了不同反压下隔离段出口温度、压力及马赫数间的拟合式,给出了预估任意反压下,隔离段出口马赫数和温度的方法;研究了隔离段最大承受反压与无反压下隔离段出口马赫数的关系,分别给出了均匀来流和非均匀来流时隔离段最大承受反压的拟合关系式,为最大反压比的估算提供了方法;同时还给出了均匀来流条件下等直隔离段长高比的工程选取拟合式。     

太阳风与彗尾等离子体相互作用引起不稳定的一种讨论

本文讨论了在无力场情形下,太阳风与彗尾等离子体相互作用的二流不稳定问题。应用International Cometary Explorer(ICE)飞行器对彗星Giacobini-Zinner的探测数据,采用合理的等离子分布形式,得出的结论是在彗星内部存在着这种二流不稳定现象。      

最优两脉冲行星际轨道转移优化算法

 研究了最优两脉冲轨道转移问题。以行星际飞行为背景,结合状态转移矩阵和古典变分理论,推导了两脉冲行星际轨道转移的性能指标对可调参数的解析偏导数,并利用这些解析偏导数提出了一种快速的两脉冲轨道转移优化算法。解决了传统两脉冲行星际转移轨道优化算法中存在的计算速度慢,无法控制计算精度的问题。最后,以地球-火星轨道转移为例,将提出的优化算法计算的结果与传统的“能量等高线法”的计算结果进行对比,验证了此算法的正确性和快速性。     

太阳高纬探测器的借力飞行轨道设计

行星借力飞行技术可以节省深空探测任务的能量消耗.针对借助内行星引力向太阳高纬度发射探测器这一科学任务,分别以金星和地球为借力星体,运用圆锥曲线拼接法,通过求解兰伯特问题绘制能量等高线图,搜索多天体交会发射机会,设计探测器与借力体轨道周期之比为1∶ 1或2∶ 3的多次借力行星际轨道,获得相对黄道面成大倾角的目标轨道.分析表明,采用多天体交会借力相比单天体借力可大大降低发射能量;3次借用金星或者地球的引力可以使探测器轨道相对黄道面的倾角达到30°左右;3次地球借力轨道性能为最优,需要的地球发射能量更低,而且飞行器进入目标轨道之前的转移时间较短.      

改进的Tour-Map借力飞行图形设计方法

针对借力飞行轨道初始设计阶段的任务需求,提出一种改进的Tour-Map借力飞行图形设计方法,用于分析借力效果,确定借力方案和设计参数初值.在圆锥曲线拼接假设基础上,建立了借力飞行超越速度矢量和借力天体位置、速度的几何模型,推导了借力后日心轨道要素的解析表达式,并将分析结果绘制成经纬度坐标的Tour-Map轨道要素等高线图,图中综合了借力飞行后大量可行的日心转移轨道信息,为分析借力飞行的作用提供了形象的参考.将其应用在木星借力太阳高纬度探测轨道设计中,证明了方法的有效性和实用性.     

Magnetic Reconnection Phenomena In Interplanetary Space

Interplanetary magnetic reconnection(IMR) phenomena are explored based on the observational data with various time resolutions from Helios, IMP-8, ISEE3, Wind, etc. We discover that the observational evidence of the magnetic reconnection may be found in the various solar wind structures, such as at the boundary of magnetic cloud, near the current sheet, and small-scale turbulence structures, etc. We have developed a third order accuracy upwind compact difference scheme to numerically study the magnetic reconnection phenomena with high-magnetic Reynolds number (R _M=2000–10000) in interplanetary space. The simulated results show that the magnetic reconnection process could occur under the typical interplanetary conditions. These obtained magnetic reconnection processes own basic characteristics of the high R _M reconnection in interplanetary space, including multiple X-line reconnection, vortex velocity structures, filament current systems, splitting, collapse of plasma bulk, merging and evolving of magnetic islands, and lifetime in the range from minutes to hours, etc. These results could be helpful for further understanding the interplanetary basic physical processes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nonthermal effects on the cylindrical dusty ion shocks in nonthermal viscous space plasma

The propagating cylindrical shock dust ion wave (CDISW) in dusty four component plasma with three viscous component (ion and two polarity charged grains) has been introduced. The three dimensional (3D) Cylindrical Burgers (CB) equation is derived. The propagating cylindrical shock characteristics are established to becomes a very significantly improved by the supports of electron nonthermality, ion and negative (positive) kinematics viscosity coefficients. Furthermore, the shock strength depends on cylindrical directions. The obtained results may be profitable in understanding both the laboratory and space applications of plasmas.     

Propagation of normal and faster CMEs in the interplanetary medium

We have analyzed 101 Coronal Mass Ejection (CME) events and their associated interplanetary CMEs (ICMEs) and interplanetary (IP) shocks observed during the period 1997–2005 from the list given by Mujiber Rahman et al. (2012). The aim of the present work is to correlate the interplanetary parameters such as, the speeds of IP shocks and ICMEs, CME transit time and their relation with CME parameters near the Sun. Mainly, a group of 10 faster CME events (V_INT > 2200 km/s) are compared with a list of 91 normal events of Manoharan et al. (2004). From the distribution diagrams of CME, ICME and IP shock speeds, we note that a large number of events tends to narrow towards the ambient (i.e., background) solar wind speed (∼500 km/s) in agreement with the literature. Also, we found that the IP shock speed and the average ICME speed measured at 1 AU are well correlated. In addition, the IP shock speed is found to be slightly higher than the ICME speed. While the normal events show CME travel time in the range of ∼40–80 h with a mean value of 65 h, the faster events have lower transit time with a mean value of 40 h. The effect of solar wind drag is studied using the correlation of CME acceleration with interplanetary (IP) acceleration and with other parameters of ICMEs. While the mean acceleration values of normal and faster CMEs in the LASCO FOV are 1 m/s², 18 m/s², they are −1.5 m/s² and −14 m/s² in the interplanetary medium, respectively. The relation between CME speed and IP acceleration for normal and faster events are found to agree with that of  and  except slight deviations for the faster events. It is also seen that the faster events with less travel time face higher negative acceleration (>−10 m/s²) in the interplanetary medium up to 1 AU.     

怀念恩师钱学森

作者从初见钱学森的印象、在工程力学研究班学习、从事早期卫星准备工作、合作进行远程星际航行后续研究、航天名词规范及航天科普宣传等多方面,回忆了钱学森对自己的引导、指导和教导。