II型超新星瞬发爆炸模型的激波传播

本文专门讨论II型超新星瞬发爆炸模型中的激波形成点、激波波阵面的位置、激波速度和激波能量等一系列的问题 .研究发现在外星核区除存在首级激波外 ,还存在次级激波 ;激波波阵面的准确位置应在熵变化的最大点和外星核区中人为粘性压的最大点之间 ;并给出激波能量的不同定义量之间的大小关系     

Ⅱ型超新星瞬发爆炸模型的激波传播

本专门讨论Ⅱ型超新星瞬发爆炸模型中的激波形成点，激波波阵面的位置、激波速度和激波能量等一系列的问题，研究发现在外星核区除存在首级激波外，还存在次级激波，激波波阵面的准确位置应用熵变化的最大点和外星核区中人为粘性压的最大点之间，并给出激波能量的不同定义量之间的大小关系。     

多方气体球引力坍缩中激波的形成和传播

本文采用计算流体力学中的高分辨率ＰＰＭ格式，数值模拟了多方气体球的引力坍缩、激波形成和传播。物态方程取成ｐ＝Ｋ（ｓ）ρ＾γ，γ为密度的分段函数，通过绝热指数γ的不同取法对三个模型分别进行了计算，并对引力坍缩、反弹激波形成和传播等三个过程及不型之间计算结果的一些差异做了比较仔细的分析，得到了一些初步结论。     

多方气体球引力坍缩中激波的形成和传播

本文采用计算流体力学中的高分辨率ＰＰＭ格式，数值模拟了多方气体球的引力坍缩、激波形成和传播，物态方程取成Ｐ＝Ｋ（ｓ）ργ，γ为密度的分段函数，通过绝热指数γ的不同取法对三个模型分别进行了计算，并对引力坍缩、反弹激波形成和传播等三个过程以及不同模型之间计算结果上的一些差异做了比较仔细的分析，得到了一些初步结论。     

新前身星模型对超新星爆发的影响

采用2002年Woosley给出的前身星模型,使用"WZYWS9"程序数值模拟了质量为11-40M⊙的Ⅱ型超新星的爆发过程.计算结果显示新模型对Ⅱ型超新星塌缩、激波传播及爆发都有不同程度的影响.此外,还讨论了激波初始能量的定义.     

奇异夸克相变对II型超新星激波能量的影响

在模拟超新星演化时,考虑非奇异－奇异夸克相变因素,与没有考虑奇异相变的情况相比,得到了更强的激波,这可能是奇异相变增加了星核区对流不稳定性所致,在本的计算环境里,一阶奇异夸克相变的结果使具有１．２８Ｍ铁星核的ＷＷ（８８）模型爆发,打破了瞬发机制只能使约１．１Ｍ铁星核模型爆发的上限,并支持了戴子高等人所作出的奇异夸克相变能超新爆发机会的论断。     

星际无碰撞激波的Balmer双线结构

Balmer发射线是研究星际无碰撞激波物理性质的重要途径之一.星际无碰撞激波的Balmer发射线包括宽线和窄线两个明显的成分.通常认为,这种双线成分是与激波联系在一起的,宽线产生于激波前慢中性粒子与激波后高能质子的电荷交换,反映了激波后粒子的热运动状况,而窄线则产生于激波前慢中性粒子的激发,反映了激波前粒子的热运动状况.但是,近来更细致的观测和理论计算表明,超新星遗迹中Balmer发射线的双线结构很可能还要受到其他因素的影响,并且与激波速度和电子-质子的热平衡有着密切的关系.该文将讨论影响Balmer双线结构的各种因素,并讨论Balmer双线结构在超新星遗迹研究中的一些应用.     

内激波火球中e±的产生、湮灭及再辐射

在内激波伽玛暴(GRB)模型下,中心能源喷出一系列质量相当但整体Lorentz 因子相差悬殊的物质壳层,这些先后快慢的壳层发生激烈的碰撞并产生相对论性的激波,壳层中的电子被激波加热后通过同步辐射和逆康普顿散射发射高能γ光子.对于能量高达GeV的高能光子(观测者系)可能因为γ-γ碰撞产生电子对而被火球吸收.Pilla和Leob数值计算发现产生的电子对数目远高于火球本身的电子数目,Li等人最近也得到了类似的结果并以此来解释早期余辉中缺少光学闪.通过解析研究该过程中电子对的产生与湮灭随时间的演化后,发现对于一个典型的pulse,同步高能部分产生的e±数目早期较多,湮灭率也高;在后期由于受到最大同步辐射频率的限制,该成分不再对e±的产生有贡献.与之不同,逆康普顿散射成分对e±的产生的贡献近似与pulse的持续时标成正比.在典型的参数范围下,两种成分共同作用产生的电子对数目可达原火球携带的电子数目的10来倍.由于所产生的e±的Lorentz因子较小,相应的同步辐射不会影响到观测谱(至少在BATSE探测器的能段是这样),但再次逆康普顿散射后则可能影响到观测谱.由于电子对的质量远比质子质量小,所以对后期的火球动力学演化的影响不大.至少对于均匀介质环境,电子对的存在对于早期余辉的光学辐射影响不大.     

Suprathermal Proton Bremsstrahlung: Energy Loss Rate and Radiation Modelling

Suprathermal proton bremsstrahlung (SPB) of energetic protons is an important source of high-energy X-ray and gamma-ray photons in the interstellar medium. We calculate the suprathermal bremsstrahlung radiation power and the associated energy loss rate of the radiating protons. Also the mean photon energy from the SPB process is derived which can be used to construct a monochromatic approximation of the radiation power. The SPB power is the starting point for the quantitative modelling of theoretical SPB radiation spectra in cosmic sources. This revised version was published online in July 2006 with corrections to the Cover Date.     

奇异夸克相变对II型超新星激波能量的影响

在模拟超新星演化时, 考虑非奇异奇异夸克相变因素,与没有考虑奇异相变的情况相比, 得到了更强的激波.这可能是奇异相变增加了星核区对流不稳定性所致. 在本文的计算环境里,一阶奇异夸克相变的结果使具有1.28 M铁星核的WW(88)模型爆发,打破了瞬发机制只能使约1.1 M铁星核模型爆发的上限,并支持了戴子高等人所作出的奇异夸克相变能提高超新星爆发机会的论断.     

Propagation of the Bastille Day 2000 CME Shock in the Outer Heliosphere

The Bastille Day (14 July) 2000 CME is a fast, halo coronal mass ejection event headed earthward. The ejection reached Earth on 15 July 2000 and produced a very significant magnetic storm and widespread aurora. At 1 AU the Wind spacecraft recorded a strong forward shock with a speed jump from ∼ 600 to over 1000 km s⁻¹. About 6 months later, this CME-driven shock arrived at Voyager 2 (∼ 63 AU) on 12 January 2001 with a speed jump of ∼ 60 km s⁻¹. This provides a good opportunity to study the shock propagation in the outer heliosphere. In this study, we employ a 2.5-D MHD numerical model, which takes the interaction of solar wind protons and interstellar neutrals into account, to investigate the shock propagation in detail and compare the model predictions with the Voyager 2 observations. The Bastille Day CME shock undergoes a dramatic change in character from the inner to outer heliosphere. Its strength and propagation speed decay significantly with distance. The model results at the location of Voyager 2 are in good agreement with in-situ observations. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1014293527951     

Effects of Dust on the Propagation of Shock Waves in Circumstellar Envelopes of Late-Type Variable Stars

Physical processes affecting propagation of moderate-strength shocks in the inner parts of circumstellar envelopes of Miras are considered. In particular, the influence of dust, which is heated later than heavy gas particles, is critical for pumping of circumstellar H₂O masers. Strong shocks with Mach numbers M exceeding ∼ 10 destroy dust and molecules and partly ionize the gas. Weaker shocks with 3 < M < 10 spend their energy mainly to dissociate molecules. Shocks with 1 < M < 3 lose their energy via heating of dust and may stimulate formation of dust. Some implications are discussed. This revised version was published online in September 2006 with corrections to the Cover Date.     

Propagation of Extremely Low Frequency Waves Through the Ionosphere

The propagation features of extremely low frequency electromagnetic waves through the multicomponent ionospheric plasma are studied. It is shown that at relatively lower frequencies refractive index for right hand mode is higher than the left-hand mode, which is reversed at higher frequencies. The thermal temperature of plasma particle causes decrease in phase and group velocities of both right and left-hand modes. The crossover frequencies for different plasma models are computed and variation with ion concentration and thermal velocity is studied. Explicit expression for group velocity and travel time has been derived and studied numerically. Finally, we have presented simulation of the ion whistler spectrograms for Hydrogen, Helium and Oxygen ions present in the ionospheric plasma. The results are compared with the experimentally detected hydrogen and helium ion whistlers. The importance of the present study in the exploration of ionospheric plasma is illustrated.     

The Effect of Direct Solar Radiation Pressure on a Spacecraft of Complex Shape

An analytical solution for the joint effects of the Earth oblateness and the direct solar radiation pressure on the motion of an Artificial Earth Satellite of complex shape is constructed. The equations of motion are derived in the previous paper (hereafter refered to as paper I). The solution is effected through two canonical transformations retaining secular and periodic terms up to orders 3 and 2 respectively. The developments stressed on the effects of the radiation pressure and its coupling with the earth's gravity. A procedure for the computation of position and velocity is outlined. The conditions of the resonance are determined and the procedure for the transformations in the case of resonance is outlined. The solution revealed as expected that radiation pressure produced secular effects at the third order resulting from the coupling between periodic terms at lower orders. These affect both the main satellite body and the antenna. This revised version was published online in July 2006 with corrections to the Cover Date.     

Propagation of whistler mode ion-cyclotron wave through multicomponent plasma

The dispersion relation of an ion cyclotron wave propagating through a multicomponent plasma including the effect of ion thermal velocity is analysed and an analytical expression for the group travel time, and the temporal and spatial damping rate is derived. It is shown that the temporal and spatial damping rate increases with temperature and group travel time. The inclusion of thermal effect in group travel time causes a reduction in damping rate. The results are important in the study of the proton whistler propagating through the ionosphere.