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1.
本文通过数值求解带电粒子与Ａｌｆｖｅｎ波湍动相互作用的动力学方程，得到了相对论电子在射电喷流中被加速随时间演化的解．高能电子可以加速到Ｌｏｒｅｎｔｚ因子γｙ～１０６，且形成稳态的幂律谱，尽管其谱指数Ｓ≈ｌ比观测值小，但粒子加速时间约为１０１２－１０１４秒，小于射电斑的寿命１０７年．粒子能谱指数几乎与Ａｌｆｖｅｎ波谱指数和能量损失函数无关．能量损失对加速上限有较大影响． 相似文献
2.
空间尘埃等离子体Maser效应以及所导致的Langmuir辐射 总被引：1，自引：0，他引：1
本从弱湍动等离子体理论出发,由Ｖｌａｓｏｖ方程导出Ｍａｓｅｒ效应作用机制下共振波的演化规律,并且讨论了尘埃等离子体电子束入射情况下,共振Ｌａｎｇｍｕｉｒ波的增长率,研究结果表明,Ｍａｓｅｒ效应比其它不稳定性（如本中论及的束流不稳定性等）能更好的解释空间中反常Ｌａｎｇｍｕｉｒ辐射现象。 相似文献
3.
本文从弱湍动等离子体理论出发,由Ｖｌａｓｏｖ方程导出了Ｍａｓｅｒ效应作用机制下共振波的演化规律;并且讨论了尘埃等离子体电子束入射情况下,共振Ｌａｎｇｍｕｉｒ波的增长率．研究结果表明,Ｍａｓｅｒ效应比其它不稳定性（如本文中论及的束流不稳定性等）能更好地解释空间中的反常Ｌａｎｇｍｕｉｒ辐射现象． 相似文献
4.
程久恒 《中国天文和天体物理学报》1994,(3)
从细磁通量管运动方程组导出了特征速度、特征线及其相容关系。这些结果是用特征线法研究细磁通量管运动的基础，也是正确提出定解问题的依据。表征细磁通量管横向波传播的特征速度与管内流动的ＡｌｆｖｅｎＭａｃｈ数有关。当管内流速超过ｋｅｌｖｉｎ－Ｈｅｌｍｈｏｌｔｚ不稳定性临界值时，不存在横向波模式。 相似文献
5.
从细胞量运动方程组导出了特征速度，特征线及其相容关系，这些结果是用特征线法研究细磁通量管运动的基础，也是正确提出定解问题的依据。表征细磁通量管横向波传播的特征速度与管内流动的Ａｌｆｖｅｎ Ｍａｃｈ数有关，当管内流速超过Ｋｅｌｖｉｎ－Ｈｅｌｍｈｏｌｔｚ不稳定性临界值时，不存在横向波模式。 相似文献
6.
在柱坐标下将黑子周围的环形区域（黑子除外）内的振荡分解为朝向黑子传播的（入射的）波和离开黑子传播的（出射的）波。对无黑子的环形区域内的振荡也进行了同样的分解。将黑子周围的入射波看成是被黑子磁流管磁化了的介质（介质内的磁场基本是水平的）中的波。而无黑子区的入射波看成是非磁化介质中的波。比较这两种波在固定波数下功率随频率的分布发现，在磁化介质中不同径向除ｎ的声波（ｐ模）频率系统降低，同时功率也降低，降低的功率最高达非磁化介质中波的功率的３０％。而比较在固定频率下功率随波数的分布发现，磁场中ｆ模及ｎ＝１，２，３的ｐ模的脊向高波数方向位移，功率的降低受频率调制，即声波在某些有限的频带中被吸收。这些观测表明，在磁场中ｐ模与磁声重力波（ＭＡＧ）产生了模式混合或耦合。模式混合的存在支持了模式转换作为ｐ模式被黑子吸收的机制的解释。此外，本文还分析了转换的ＭＡＧ波进入黑子磁流管（其中的磁场基本上是垂直的）后进一步被吸收，吸收的功率最高达ＭＡＧ波的２０％。在磁流管内没有进一步观测到模式的转换 相似文献
7.
本文对相对论电子的辐射性质、能谱演化和加速机制等进行了简要的介绍。同时，对相对论电子在高能天体中的辐射作用和特性进行了简要的综述。本文给出了相对论电子在Blazar天体的射电辐射机制、光变机制、BL Lac天体的辐射机制以及γ暴的辐射机制等方面的应用研究成果。1、提出了相对论电子的光学薄同步辐射模型：解释Blazar天体的射电平谱：Blazar中心体的剧烈活动，使射电辐射区处于等离子体湍动状态，其中的相对论电子在湍动等离子体波的二交费米加速、激波加速、辐射损失、粒子逃逸和辐射区的绝热减速等物理过程作用下，形成较平的能谱，产生射电平谱。2、提出了新的Blazar天体光变模型：当Blazar天体爆发时，中心天体产生大量的相对论电子，注入喷流中；相对论电子产生同步辐射，并不断损失能量和逃逸辐射区，使它们的能谱快速变化，引起辐射发生快速光变。3、给出了BL Lac天体的等离子体反应堆模型：大量相对论电子从中心天体注入周围的等离子体反应堆中，通过同步辐射快速损失能量，同时这些电子同步吸收反应堆中不透明的光子，产生一个稳定、各向同性的幂律分布，其谱指数为γ＝3；然后，这些相对论电子通过等离子体反应堆的爆发或其表面扩散过程逃逸出来，辐射低频的同步辐射。模型解释了BL Lac天体的高频辐射表现出快速的谱变化性质，即流量减小时谱变陡。4、提出了相对论电子的内激波加速模型，解释γ暴的尖峰光变特性：在γ暴产生的相对论运动的壳层中，有内激波产生；激波在壳层中传播，耗散壳层的运动能，使其中的部分电子加速成为相对论电子。然后，这些电子通过同步辐射产生观测到的γ辐射。模型认为，γ暴中的每个尖峰辐射是一对内激波加速相对论电子的辐射过程，复杂的γ暴光变曲线是多对内激波辐射过程的叠加。 相似文献
8.
弱磁化相对论电子束注入等离子体时，由非共振波粒相互作用激发的束－等离子体不稳定性可以直接放大电磁波。计算结果表明：在偏离共振条件的区域，电磁波仍可在较宽的频率范围被放大，并在每个共振峰下形成平台结构。随着谐波数的增高，增长率峰值逐渐变小，峰宽也变窄。本还分析了电磁波的增长率随背景参数ｗｐｅ／Ｑｅ及高能电子的入射方向和辐射方向的变化规律。在典型的日冕条件下，此类不稳定性所放大的电磁波的增长率大小、 相似文献
9.
一般认为，Langmuir波转换为电磁波是太阳射电Ⅲ型暴的重要机制，由电子束流不稳定性可以很容易的激发Langrnuir波。正向Langmuir波和反向Langmuir波的相互作用被认为是产生静电的高次谐波的原因之一。本文对于含有温度的双流不稳定性的方程进行了解析求解，发现了温度和柬流速度分别对于K〉0时Langmuir波色散关系具有显著的影响，进而采用了粒子模拟的方法，进一步证实了解析推导的结果。 相似文献
10.
利用国家天文台云南天文台“分米波(700—1500MHz)射电频谱仪”和“四波段太阳射电高时间分辨率同步观测系统”分别于2001年6月24日和1990年7月30日观测到了两个稀少事件，前者是一个小射电爆发，其上升相伴随有短周期(约29、40和100毫秒)的脉动，后者是一个射电大爆发，在2840MHz上产生了周期约30毫秒的射电脉动，还着重讨论其甚短周期(如29—40毫秒)的脉动现象，甚短周期脉动可能是归因于起源在日冕深处不稳定区域的哨声波束周期链对射电辐射的调制，或沉降电子束驱动的静电高混杂波，经由波-波非线性相互作用导致甚短周期的射电脉动。 相似文献
11.
The equation of small oscillations of ULF waves in the Earth’s magnetosphere is derived accounting for a fast magnetosonic wave. The spectrum of discrete Alfven modes near the Alfven frequency minimum is studied on the basis of this equation. 相似文献
12.
Yu. T. Tsap 《Bulletin of the Crimean Astrophysical Observatory》2012,108(1):46-51
The continuous reflection of Alfven waves in the coronae of the Sun and stars is considered. Based on the WKB approximation, the solution to the linear wave equation in the case of a stratified isothermal atmosphere has been obtained. A critical analysis of results obtained by Ferraro and Plumpton (1958) and Hollweg (1972), as well as the relations in the Elsasser variables has been carried out. It has been shown that Alfven disturbances do not undergo a continuous reflection within the accepted model and are transformed into intermediate-type modes that possess the properties of vibrations and travelling waves. The problem of the turbulization of corona plasma is discussed. The origin of the Alfven waves that propagate toward the Sun is related to the development of parametric instability. 相似文献
13.
本文根据波与介质相互作用的一套全MHD方程组,计算了无碰撞阿尔文波波能密度W和波能耗散项E_m,在太阳过渡区和内冕大气中随高度的分布。 计算结果表明:对于温度、密度偏低的大气,在过渡区底部几十甚至几百公里范围内,无碰撞阿尔文波的耗散引起的对大气的加热可超过热传导的贡献。从而说明这种阿尔文波的加热似乎是引起温度、密度偏低的大气(例如冕洞大气)在过渡区中温度陡升的重要原因。 相似文献
14.
《Chinese Astronomy and Astrophysics》2005,29(2):136-148
The method of Orthogonal Function Series Expansion (OFSE) is generalized and applied to the study of the evolution of the coupling of nondissipative torsional Alfven wave and fast wave in coronal loops. Using this method, the intrinsic angular frequency of the overall wave mode can be described mathematically and that of the Alfven waves along the magnetic lines in the coronal loop during the coupling of the Alfven and fast waves can be analyzed both theoretically and numerically. Also with this method, the relation between the coupling driven term and the Alfven wave resonance may be analyzed. Results of computation reveal the place of appearance of coupling resonance as well as the characteristics of the amplitudes of the Alfven and fast waves. As found by the calculations, if the footpoint driven angular frequency is not equal to the intrinsic angular frequency of the overall wave mode of the coronal loop and when a δ section appears at the place of coupled resonance, the radial gradient of the fast wave's amplitude is quite large. Sometimes it approximates to a discontinuity, and this is extremely favorable for the dissipation of the fast wave. If the footpoint driven angular frequency is equal to the intrinsic angular frequency of the overall wave mode and when a δ section occurs in the Alfven wave amplitude, abundant small-scale structures appear in the radial direction. Then the location of resonance approximately becomes a discontinuity, very favorable to the dissipation of the Alfven wave. 相似文献
15.
《Planetary and Space Science》2007,55(4):467-474
A theoretical study is made on the generation mechanism of electrostatic Bernstein mode wave in the presence of electromagnetic Kinetic Alfven wave turbulence in magnetized inhomogeneous plasma on the basis of plasma-maser interaction. It is shown that a test high-frequency electrostatic Bernstein mode wave is unstable in the presence of low-frequency Kinetic Alfven wave turbulence. Because of the universal existence of the Kinetic Alfven waves in large-scale plasmas, the result has potential importance in space and astrophysical radiation process. The growth rate of the test high-frequency Bernstein mode wave is obtained with the involvement of spatial density gradient parameter. A comparative study on the role of density gradient in the generation of Bernstein mode on the basis of plasma-maser effect is presented. 相似文献
16.
《Chinese Astronomy and Astrophysics》1984,8(2):157-161
The propagation of the Alfven waves in a plasma stream with a non-uniform density distribution is considered. It is shown that the density inhomogeneity will cause self-scattering of the wave. A longitudinal magnetic field component will be generated and part of the energy of the wave will propagate in directions deviating from the given mean magnetic field. Thus, to explain certain observed features of the solar wind, it is not necessary to appeal to a mixture of Alfvenic and magnetosonic modes. 相似文献
17.
The particle aspect approach is adopted to investigate the trajectories of charged particles in the electromagnetic field of kinetic Alfven wave. Expressions are found for the dispersion relation, damping rate and associated currents in homogenous plasma. Kinetic effects of electrons and ions are included to study kinetic Alfven wave because both are important in the transition region. It is found that the ratio β of electron thermal energy density to magnetic field energy density and the ratio of ion to electron thermal temperature (Ti/Te) affect the dispersion relation, damping-rate and associated currents in both cases (warm and cold electron limits). The treatment of kinetic Alfven wave instability is based on the assumption that the plasma consists of resonant and non-resonant particles. The resonant particles participate in an energy exchange process, whereas the non-resonant particles support the oscillatory motion of the wave. 相似文献
18.
We look at time-dependent normal mode solutions to the Alfven wave equation in a uniform magnetic field, between planar ionospheres. In particular, the effect of sharp gradients in ionospheric conductivity on the spatial and temporal structure of the waves is considered. We show that the electric field of the wave must always be perpendicular to any conductivity discontinuities present, and that this is achieved by the generation of circularly polarized Alfven waves at the discontinuity. The results are applied to an ionospheric strip of high conductivity; this being relevant to Pi2s. 相似文献
19.
观测表明, 黑洞双星的B型准周期振荡(Quasi-Periodic Oscillation, QPO)频率与幂律通量之间存在正相关性. 试图基于阿尔文波振荡模型定量解释该相关性. 标准薄吸积盘辐射通量极大值处的阿尔文波振荡产生QPO. 标准薄盘上的软光子与冕或喷流基部的热电子介质发生逆康普顿散射产生幂律通量. 通过吸积率的连续变化, 得到QPO频率与幂律通量关系的分析解和数值解. 模拟得到的相关性在合理的参数范围内与观测值相吻合. QPO频率与幂律通量的正相关性可以理解为, 较强的磁场导致较高的阿尔文波频率和较高的电子温度从而得到较高的幂律通量. 结果表明B型QPO可能与吸积盘或喷流中的环向磁场的活动有关. 相似文献
20.
Daniel Atnafu Chekole Gebretsadikan Woldmhret Bahta 《Journal of Astrophysics and Astronomy》2018,39(6):67
Magnetohydrodynamics waves and instabilities in rotating, self-gravitating, anisotropic and collision-less plasma were investigated. The general dispersion relation was obtained using standard mode analysis by constructing the linearized set of equations. The wave mode solutions and stability properties of the dispersion relations are discussed in the propagations transverse and parallel to the magnetic field. These special cases are discussed considering the axis of rotation to be in transverse and along the magnetic field. In the case of propagation transverse to the magnetic field with axis of rotation parallel to the magnetic field, we derived the dispersion relation modified by rotation and self-gravitation. In the case of propagation parallel to the magnetic field with axis of rotation perpendicular to the magnetic field, we obtained two separate modes affected by rotation and self-gravitation. This indicates that the Slow mode and fire hose instability are not affected by rotation. Numerical analysis was performed for oblique propagation to show the effect of rotation and self-gravitation. It is found that rotation has an effect of reducing the value of the phase speeds on the fast and Alfven wave modes, but self-gravitation affect only on the Slow modes, thereby reducing the phase speed compare to the ideal magneto hydrodynamic (MHD) case. 相似文献