共查询到18条相似文献，搜索用时 49 毫秒
1.
电子是太阳风粒子中最为重要的组分之一,它可以通过多种机制对太阳风产生影响.太阳风中的电子通常具有温度各向异性和束流两种非热平衡分布特征,这些偏离热平衡分布的特征可以通过波粒相互作用激发电子不稳定性和等离子体波动,激发的等离子体波动又可以通过波粒相互作用调制太阳风粒子的分布,从而加热太阳风中的背景粒子.因此电子动力学不稳定性在太阳风的演化过程中扮演了极为重要的角色.详细介绍了太阳风中常见的电子动力学不稳定性,并基于等离子体动力论,详细介绍太阳风传播过程中所出现的各种不稳定性,尤其是在近日球层和太阳大气区域所出现的电子声热流不稳定性以及低混杂热流不稳定性,并分析其波粒相互作用机制,以便更加深入地研究太阳风传播过程中的电子分布函数演化. 相似文献
2.
动力学阿尔文波是垂直波长接近离子回旋半径或者电子惯性长度的色散阿尔文波.由于波的尺度接近粒子的动力学尺度,动力学阿尔文波在太阳和空间等离子体加热、加速等能化现象中起重要作用.因此,动力学阿尔文波通常被认为是日冕加热的候选者.本研究工作深入、系统地调研了太阳大气中动力学阿尔文波的激发和耗散机制.基于日冕等离子体环境,介绍了几种常见的动力学阿尔文波激发机制:温度各向异性不稳定性、场向电流不稳定性、电子束流不稳定性、密度非均匀不稳定性以及共振模式转换.还介绍了太阳大气中动力学阿尔文波的耗散机制,并讨论了这些耗散机制对黑子加热、冕环加热以及冕羽加热的影响.不仅为认识太阳大气中动力学阿尔文波的驱动机制、动力学演化特征以及波粒相互作用提供合理的理论依据,而且有助于揭示日冕等离子体中能量储存和释放、粒子加热等能化现象的微观物理机制. 相似文献
3.
正电磁离子回旋波是指频率低于或者接近离子回旋频率的电磁波,其存在左旋和右旋两种偏振状态.通过回旋共振相互作用,电磁离子回旋波能直接与粒子发生能量交换,对太阳风等离子体加热和加速等能化现象起着重要作用.然而,太阳风中电磁离子回旋波的激发机制及其波粒相互作用尚未完全清楚.本学位论文深入、系统地研究了太阳风等离子体环境下离子束流对电磁离子回旋波激发机制的影响及其波粒相互作用,为进一步理解与解释太阳风中微观等离子体物理过程、 相似文献
4.
本文试图利用等离子体的堆垒效应及波-粒子非共振加热机制对太阳色球-日冕过渡层出现的温度随高度陡分布现象提出定性定量的说明。分析表明,只要有一高能质子束从色球注入过渡层,通过等离子体波-粒子非线性相互作用,就能使温度在窄区域中出现陡分布。 相似文献
5.
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
6.
动力学阿尔文波是垂直波长接近离子回旋半径或电子惯性长度时的色散阿尔文波,在等离子体粒子加热、加速或反常输运等现象中能起重要作用.因此,在各类天体和空间等离子体环境中动力学阿尔文波的特性也一直是引起人们广泛兴趣和倍受关注的研究课题.本论文系统、深入地研究了不同等离子体环境下动力学阿尔文波的非线性波一波耦合相互作用过程,特别是对不同环境下波一波耦合导致的动力学阿尔文波非线性生长率进行了细致的分析. 相似文献
7.
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。本文还分析了电磁波的增长率随背景参数ω＿（ｐｅ）／Ω＿ｅ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、带宽、方向性、偏振及谐波等性质，可以用来解释太阳Ⅲ型射电爆发现象，本文的研究亦可用来解释其他天体等离子体辐射。 相似文献
8.
不稳定性和频谱演化──再论等离子体辐射与其它辐射机制的关系 总被引：1，自引：0，他引：1
本文力图阐明的一个基本观点是:由等离子体不稳定性所激发的电磁波幅度的增长从本质上揭示了辐射过程内部的波粒相互作用对辐射频谱演化的贡献。因此,等离子体辐射理论是建立在经典电动力学的辐射理论的基础之上,并以各种基本辐射过程(如轫致辐射、回旋及同步辐射等)的平衡态为初始条件,从而发展起来的动态辐射理论。 相似文献
9.
太阳风中的电磁离子回旋(Electromagnetic Ion Cyclotron, EMIC)波自报道以来,受到了广泛的关注和研究.由于波的频率接近质子的回旋频率, EMIC波可以通过回旋共振波粒相互作用将波能传递给离子,并在太阳风粒子加热和加速等能化现象中发挥重要作用.总结了太阳风中EMIC波的观测和理论研究进展,包括EMIC波在磁云内外、磁云和行星际日冕物质抛射鞘区中的观测研究得到的一系列结果以及基于观测进行波的激发机制所取得的研究进展,并展望未来研究太阳风中EMIC波的突破方向. 相似文献
10.
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
11.
V. Krishan 《Solar physics》1978,59(1):29-42
Three different mechanisms are suggested for the non-linear saturation of the ion-acoustic instability. These include the indirect wave-particle interaction, the scattering on density fluctuations and the effects of energy renormalization of the particles. A comparison with the earlier theoretical investigations and the recent observations of Skylab has been made. 相似文献
12.
The ionization of hydrogen atoms that penetrate into the heliosphere from the interstellar medium gives rise to a peculiar population of energetic protons (interstellar pickup protons) in the solar wind. The short-wavelength Alfvènic turbulence in the outer heliosphere is entirely attributable to the source associated with the instability of the initial anisotropic pickup proton velocity distribution. The bulk of the generated turbulent energy is subsequently absorbed by the pickup protons themselves through the cyclotron-resonance particle-wave interaction, and only an insignificant fraction of this energy can be transferred to the solar wind protons and heat them up. 相似文献
13.
K. L. Vithal 《Astrophysics and Space Science》1977,49(2):317-330
Growth rates for both the RH- and LH-modes of an EM wave propagating along a magnetic field through an isotropic loss-cone plasma have been obtained. It is found that growing modes can exist, and are found to depend critically on the mirror ratioR, and the specific details of the distribution function of the energetic component. To study the energetic-particle distribution observed at low energies by satellites within the magnetosphere, an isotropic double-humped loss-cone velocity distribution is then studied with a view to determining whether the secondary hump can introduce an instability not present for monotonic distribution. It is found that such a distribution can be unstable in a mirror geometry if the energetic component is sufficiently monoenergetic. Within the magnetosphere, nearly monoenergetic fluxes are observed, peaking in the energy range 1–10 keV, depending on the McIlwain parameterL. It is possible that the initial injection of monoenergetic particles may have been much more sharply peaked than the one presently observed, and, as a result of wave-particle interactions, subsequently relaxed to the presently observed distribution. It is seen here that the EM waves within the magnetosphere can contribute to the relaxation of such an initial injection. 相似文献
14.
《Chinese Astronomy and Astrophysics》2005,29(1):1-8
On the basis of an analysis of the instability of drift caused by density and magnetic field inhomogeneities in plasmas with finite β, the effect of the instability on the excitation of kinetic Alfven wave (KAW) is probed. In the kinetic theory, which correctly treats the effect of the finite Larmor radius and the wave-particle resonant interaction, the motion of the ions is described with the Vlasov equation and the motion of electrons, with the kinetic drift equation. Comparing the effects by inhomogeneities in the density and in the magnetic field in plasmas with finite β, we found that the drift instability is more easily excited by the former, and in the instability so excited, the energy transfer is more intense. This energy transfer provides the physical basis for the excitation of KAW. As shown by numerical solutions, KAWs can be widely excited and produced in the magnetosphere, especially in the cusp of the magnetosphere, in the magnetopause and in the boundary layers of plasma sheets, where inhomogeneities are obvious. The results of the present work further illustrate that the KAW plays an important role in the energy transfer in magnetospheric regions. 相似文献
15.
S. Y. Kim 《Astrophysics and Space Science》1990,167(1):21-27
Recently various waves and particle observations of auroral field lines have been carried out by the Swedish magnetospheric research satellite Viking. In order to study wave-particle interaction extensively, waves and subsequent ion beams are measured simultaneously. Both narrowband EIC waves and wideband EIC waves of up to several times the proton gyro-frequency have been detected. Along with the observed wave characteristics, a cool low-density electron population has been detected in ion-beam regions sometimes. Therefore, we try to find an effect on EIC wave instability by the presence of cold electrons using computer simulation. 相似文献
16.
Robert F. Wimmer-Schweingruber Ralph McNutt Nathan A. Schwadron Priscilla C. Frisch Mike Gruntman Peter Wurz Eino Valtonen 《Experimental Astronomy》2009,24(1-3):9-46
The Sun, driving a supersonic solar wind, cuts out of the local interstellar medium a giant plasma bubble, the heliosphere. ESA, jointly with NASA, has had an important role in the development of our current understanding of the Suns immediate neighborhood. Ulysses is the only spacecraft exploring the third, out-of-ecliptic dimension, while SOHO has allowed us to better understand the influence of the Sun and to image the glow of interstellar matter in the heliosphere. Voyager 1 has recently encountered the innermost boundary of this plasma bubble, the termination shock, and is returning exciting yet puzzling data of this remote region. The next logical step is to leave the heliosphere and to thereby map out in unprecedented detail the structure of the outer heliosphere and its boundaries, the termination shock, the heliosheath, the heliopause, and, after leaving the heliosphere, to discover the true nature of the hydrogen wall, the bow shock, and the local interstellar medium beyond. This will greatly advance our understanding of the heliosphere that is the best-known example for astrospheres as found around other stars. Thus, IHP/HEX will allow us to discover, explore, and understand fundamental astrophysical processes in the largest accessible plasma laboratory, the heliosphere. 相似文献
17.
The physics of the heliosphere has seen several exciting developments in the past years since the in situ discovery of the termination shock by Voyager 1 at 94 AU and radio observations of the interaction of GMIRs with the heliopause. The local hydrogen wall ahead of the heliosphere has been inferred from interstellar absorption lines and information about the interstellar magnetic field is now available. This sudden richness of information has lead to a waking realisation about the importance of the heliosphere for long-term space climate and possibly even terrestrial climate. 相似文献
18.
The Interstellar Heliopause Probe: Heliospheric Boundary Explorer Mission to the Interstellar Medium
The Sun, driving a supersonic solar wind, cuts out of the local interstellar medium a giant plasma bubble, the heliosphere. ESA, jointly with NASA, has had an important role in the development of our current understanding of the Suns’ immediate neighborhood. Ulysses is the only spacecraft exploring the third, out-of-ecliptic dimension, while SOHO has allowed us to better understand the influence of the Sun and to image the glow of interstellar matter in the heliosphere. Voyager 1 has recently encountered the innermost boundary of this plasma bubble, the termination shock, and is returning exciting yet puzzling data of this remote region. The next logical step is to leave the heliosphere and to thereby map out in unprecedented detail the structure of the outer heliosphere and its boundaries, the termination shock, the heliosheath, the heliopause, and, after leaving the heliosphere, to discover the true nature of the hydrogen wall, the bow shock, and the local interstellar medium beyond. This will greatly advance our understanding of the heliosphere that is the best-known example for astrospheres as found around other stars. Thus, IHP/HEX will allow us to discover, explore, and understand fundamental astrophysical processes in the largest accessible plasma laboratory, the heliosphere. 相似文献