代数重建法反演环电流分布的初步结果

TC-2卫星携带了高能中性原子成像仪.在理论上可以根据对中性原子的探测通过反演获得磁层中环电流的空间分布.开发了一种新的反演技术和算法来反演环电流的分布.文中将层析成像技术引入反演环电流区离子分布,把磁层空间环电流区域划分为网格并依据层析成像常用的代数重建法反演环电流的分布.反演前后的电流离子分布具有一致性,证实了这种反演方法的可行性.通过对比反演结果与初始分布,模型通过较少的假设和简单的步骤就可以获得全面的环电流信息.      

Relationships between energetic storm particle events and interplanetary shocks driven by full and partial halo coronal mass ejections

We have analysed energetic storm particle (ESP) events in 116 interplanetary (IP) shocks driven by front-side full and partial halo coronal mass ejections (CMEs) with speeds $>$400 km s^?1during the years 1996–2015. We investigated the occurrence and relationships of ESP events with several parameters describing the IP shocks, and the associated CMEs, type II radio bursts, and solar energetic particle (SEP) events. Most of the shocks (57 %) were associated with an ESP event at proton energies $>$1 MeV.The shock transit speeds from the Sun to 1 AU of the shocks associated with an ESP event were significantly greater than those of the shocks without an ESP event, and best distinguished these two groups of shocks from each other. The occurrence and maximum intensity of the ESP events also had the strongest dependence on the shock transit speed compared to the other parameters investigated. The correlation coefficient between ESP peak intensities and shock transit speeds was highest (0.73 $\pm$ 0.04) at 6.2 MeV. Weaker dependences were found on the shock speed at 1 AU, Alfvénic and magnetosonic Mach numbers, shock compression ratio, and CME speed. On average all these parameters were significantly different for shocks capable to accelerate ESPs compared to shocks not associated with ESPs, while the differences in the shock normal angle and in the width and longitude of the CMEs were insignificant.The CME-driven shocks producing energetic decametric–hectometric (DH) type II radio bursts and high-intensity SEP events proved to produce also more frequently ESP events with larger particle flux enhancements than other shocks. Together with the shock transit speed, the characteristics of solar DH type II radio bursts and SEP events play an important role in the occurrence and maximum intensity of ESP events at 1 AU.     

Tearing,coalescence and fragmentation processes in solar flare current sheet and drifting pulsating structures

The paper presents a summary of results from two different simulations which study the tearing, coalescence and fragmentation of current sheets, the associated production of energetic electrons and of plasma waves from these electrons which could explain drifting pulsation structures observed at radio wavelengths. Using a 2.5-D particle-in-cell (PIC) model of the current sheet it is shown that due to the tearing mode instability the current sheet tears into plasmoids and these plasmoids later on coalesce into larger ones. During these processes electrons are accelerated and they produce observable electromagnetic waves. Furthermore, the 3-D PIC model with two current sheets extended in the electric current direction shows their fast fragmentation associated with the exponential dissipation of the free magnetic field energy. An example of the drifting pulsating structure which is considered to be a radio signature of the above mentioned processes in solar flares is shown.     

Anomalous particle transport in the heliosphere

The transport of energetic particles in the presence of magnetic turbulence can exhibit a variety of regimes different from the standard quasilinear diffusion. Here we discuss a number of solar and space problems where nonquasilinear diffusion is found, and then we illustrate anomalous transport regimes, for which the mean square deviation grows nonlinearly with time. In particular, we concentrate on superdiffusive regimes, and show what is the theoretical framework which is to be used to describe superdiffusion. We discuss the results of numerical simulations which show that superdiffusive and subdiffusive regimes are possible, and describe data analyses which allow to single out the superdiffusive transport from the observation of energetic particle profiles upstream of interplanetary shocks. The implications of superdiffusion on the efficiency of wave particle interactions are also discussed.     

The influence of in situ pitch-angle cosine coverage on the derivation of solar energetic particle injection and interplanetary transport conditions

Modelization of solar energetic particle (SEP) events aims at revealing the general scenario of SEP injection and interplanetary propagation and relies on in situ measurements of SEP distributions. In this paper, we study to what extent the LEFS60 and LEMS30 electron telescopes of the Electron Proton Alpha Monitor (EPAM) on board the Advanced Composition Explorer are able to scan pitch-angle distributions during near-relativistic electron events. We estimate the percentage of the pitch-angle cosine range scanned by both telescopes for a given magnetic field configuration. We obtain that the pitch-angle coverage is always higher for LEFS60 than for LEMS30. Therefore, LEFS60 provides more information of the directional distribution of the observed particles. The aim of the paper is to study the relevance of the coverage when fitting LEFS60 particle measurements in order to infer the solar injection and the interplanetary transport conditions. By studying synthetic electron events, we obtain that at least 70% of the pitch-angle cosine range needs to be scanned by the telescope. Otherwise, multiple scenarios can explain the data.     

Velocity correlation functions of charged particles derived from the Fokker–Planck equation

An important ingredient in theories for diffusion of charged particles across a mean magnetic field are velocity correlation functions along and across that field. In the current article we present an analytical study of these functions by investigating the two-dimensional Fokker–Planck equation. We show that for an isotropic pitch-angle Fokker–Planck coefficient, the parallel velocity correlation function is an exponential function in agreement with the standard model used previously. For other forms of the pitch-angle diffusion coefficient, however, we find non-exponential forms. Also a new, velocity correlation function based, approach for deriving the so-called Earl-relation is presented. This new derivation is more systematic and simpler than previous derivations. We also discuss higher-order velocity correlations and the applicability of the quasi-normal hypothesis in particle diffusion theory. Furthermore, we compute velocity correlation functions across the mean field and develop an alternative theory for perpendicular diffusion.     

HEDM－CMDB推进剂燃烧性能的理论预测

利用建立不久的双基系平台推进燃烧模型，对几种ＨＥＤＭ加入平台推进剂后的燃烧性能进行了理论计算。结果表明：在所计算的几种ＨＥＤＭ中，ＨＮＨＡＡ最有利于提高燃速；ＣＬ－２０最有利于降低燃速压力指数；ＣＬ－２０作为平台推进剂的高能填料综合性能最好。     

整体级发动机用叠氮含硼推进剂研究

为适应整体级发动机强制偏流喷管的需要,研究了(BAMO/THF)/HMX/AP/B叠氮含硼推进剂的工艺性能、力学性能和燃烧性能。结果表明:对营口产硼粉进行包覆、团聚处理,解决了硼粉与推进剂其它组分相容性差和推进剂工艺性能差的问题;使用经处理的硼粉、较高相对分子质量的叠氮粘合剂BAMO/THF(50/50)和高效键合剂,能有效提高含硼推进剂的力学性能,达到:常温最大抗拉强度σm≥0 7MPa,高、中、低温的最大伸长率εm≥40%;推进剂具有较低的燃速压强指数(<0 40)和较宽的燃速可调范围,118发动机演示试验后喷管收敛段和喉部结构保持完好,无凝相产物沉积,且优于HTPB含铝推进剂的结果。叠氮含硼推进剂适合整体级发动机强制偏流喷管的使用。     

核壳结构纳米铝粉热学行为

为了研究不同表面包覆物对纳米铝粉热学行为的影响,采用激光-感应复合加热法制备了三种不同表面包覆的核/壳结构纳米铝粉(氧化铝钝化、碳包覆及增塑剂DOS包覆)。采用高分辨透射电镜(HRTEM)对制备的纳米粉末结构进行表征,并采用差示扫描量热及热重分析(DSC-TG)对不同物质包覆纳米铝粉的热学性能进行研究。结果表明,这些纳米粒子均呈现出明显的核壳结构,且包覆层厚度约3.5nm。这三种不同表面包覆纳米铝粉在400℃至铝熔点(660℃)之间均发生了氧化,但非氧化物包覆纳米铝粉(碳包覆与增塑剂DOS包覆)的氧化开始温度及峰温比氧化铝钝化纳米铝粉提前了约30℃左右,而且氧化放热热焓和氧化质量增重均高于氧化铝钝化纳米铝粉,表明这两种非氧化物表面包覆对纳米铝粉的热学行为有积极的影响。最后对不同物质包覆纳米铝粉的破壳氧化机制进行了探讨。     

The elemental composition in energetic particle events at high heliospheric latitudes

The relative abundances of low energy ions (0.6–2.0 MeV/n) in solar energetic particle (SEP) and corotating interaction region (CIR) events have been measured by the EPAC experiment aboard Ulysses since launch in October 1990 until the present time. We give an overview of the abundances of heavy ions (He, C, Ne, Fe) relative to oxygen during energetic particle events lasting longer than 5 days during the in- and out-of-ecliptic phase of the mission. While the period Oct. 1990 to Aug. 1992 was dominated by high solar activity the Ulysses out of ecliptic passage at solar latitudes up to 45° went parallel to the declining phase of solar activity. Thus a very clear structure of corotating interaction regions was observed. While the in-ecliptic composition is in general agreement with measurements made near the Earth, the development of the CIR-composition shows two phases: From Aug. 1992 to May 1993 the C/O-ratio is 0.55–0.70, afterwards it increases to 0.8–0.9. This increase is correlated to the disappearance of the current sheet at 30° solar latitude reported by Smithet al. (1993).