Kinetic Theory of waves in space and astrophysical plasmas

本提案的主要目标是将在实现现有PPARC赠款（PP/D 002087/1）期间取得的理论成果扩展到与空间等离子体磁场产生的全动力学理论的发展有关的更广泛的一类物理问题。这一理论可以用来解释星系际环境中的活动星系核（AGN），微类星体，伽玛射线暴（GRB），巨大的耀斑和脉冲星风星云等关键区域的观测。这样一个理论研究的动机来自于原位卫星观测，日地等离子体和天体物理等离子体过程之间的联系的重要性，等离子体调解从天体物理源和贡献的冲击传播过程中的韦伯型不稳定性的证据。具有各向异性速度分布的无碰撞等离子体驱动广泛的不稳定性，例如离子回旋不稳定性，磁镜不稳定性，哨声和韦伯不稳定性，从而产生磁场。韦伯不稳定性存在于动量（速度）空间各向异性的均匀或近均匀等离子体中。在线性极限下，不稳定性导致等离子体中电磁场指数增长，恢复动量空间各向同性。在极端各向异性分布的极限下，韦伯不稳定性与一维或二维流不稳定性有关。在这种情况下，韦伯不稳定性是光束驱动的，有时被称为平行不稳定性。最近，这种不稳定性引起了相当大的关注，天体物理和实验室等离子体。例如，人们认为这种不稳定性可以在与各种天体物理现象相关的强无碰撞冲击波中驱动，例如，脉冲星风、伽马射线爆发和/或它们的辉光或宇宙中大尺度结构的引力坍缩。如果等离子体中存在温度梯度，也可以驱动它。由不稳定性产生的磁场是现有高能粒子的同步辐射和/或“抖动”辐射的原因。此外，这种磁场可以为带电粒子提供有效的散射机制。例如，它会影响无碰撞冲击波的耗散过程和费米加速的效率或带电粒子的热导率。在所有这些情况下，磁场的振幅是最重要的。该项目的主要目标是发展空间等离子体波动的动力学理论，将所有这些特征结合起来。本提案假定有效利用PPARC赠款PP/D 002087/1下获得的经验和成果。该项目的主要目标是：对空间等离子体中存在的各种韦伯型波模式（色散关系、增长率、不稳定阈值等）进行理论研究。包括有限的无碰撞趋肤深度，由于非麦克斯韦效应（水袋和卡帕速度分布等）电子和离子的速度分布等，研究由于外部磁场的终值的稳定的韦伯不稳定性的影响。对弱驱动和强驱动两种不同情况下的韦伯型不稳定性的非线性演化进行了解析和数值分析。阐明俘获粒子在不稳定性非线性饱和中的作用，将发展的理论应用于遥远天体物理学。将特别注意空间和天体物理物体中的粒子加速。

The main goal of the present proposal is to extend the theoretical achievements gained during realization of the existing PPARC grant (PP/D002087/1) to a wider class of physical problems related to the development of a fully kinetic theory of magnetic field generation in space plasmas. This theory may then be applied to interpret observations in such key regions of intergalactic environment as active galactic nucleus (AGNs), microquasars,gamma-ray bursts (GRBs), giant flares and pulsar wind nebulae. Motivations for such a theoretical study result from in-situ satellite observations,importance of a link between processes in solar-terrestrial and astrophysical plasmas, evidence for the plasma mediation by Weibel-type instabilities during shock propagation from astrophysical sources and contribution to fundamental plasma physics. Collisionless plasmas with anisotropic velocity distributions drive a wide class of instabilities such as ion-cyclotron instability, magnetic mirror instability, whistler and Weibel instabilities, thereby generating magnetic fields. The Weibel instability present in homogeneous or nearly-homogeneous plasmas which possess an anisotropy in momentum (velocity) space. In the linear limit the instability causes exponential growth of electromagnetic fields in the plasma which restore momentum space isotropy. In the limit of an extremely anisotropic distribution the Weibel instability is related to one or two-dimensional stream instabilities. In this situation, the Weibel instability is beam-driven, and is sometimes referred to as the filamentation instability. Recently, this instability has attracted considerable attention for both astrophysical and laboratory plasmas. For example, it is considered that this instability can be driven in strong collisionless shock waves associated with various astrophysical phenomena, e.g., pulsar winds, gamma-ray bursts, and/or theirafterglows or gravitational collapse of large-scale structures in the universe. It can also be driven if temperature gradients are present in plasmas. The magnetic field generated by the instability is responsible for synchrotron and or 'jitter' radiation from the existing high-energy particles. Furthermore, such magnetic fields can provide an effective scattering mechanism for charged particles. For example, it would affect the dissipation process of collisionless shock waves and efficiency of the Fermi acceleration or heat conductivity by charged particles. In all these cases, the amplitude of the magnetic field is of primary importance. The main goal of the project is to develop a kinetic theory of waves in space plasmas, incorporating all these features. The present proposal assumes the productive use of the experience gained and results obtained under PPARC grant PP/D002087/1. The main objectives of the project are: To perform a theoretical investigation of the various Weibel type wave modes that exist in space plasmas (dispersion relations, growth rates,instability thresholds etc.) including finite collisionless skin depth,effects due to non-Maxwellian (waterbag and kappa velocity distributions etc.) electron and ion velocity distributions etc. To study the effects of stabilization of the Weibel instability due the final value of the external magnetic field. To provide an analytical and numerical analysis of the nonlinear evolution of Weibel type instabilities in two different cases of weak and strong drive. To elucidate the role of trapped particles in the nonlinear saturation of the instability To apply the developed theory to the physics of remote astrophysical objects. Special attention will be paid to the particle acceleration in space and astrophysical objects.