Generation and Evolution of Fluctuations in a Non-equilibrium Solar Wind Plasma

对太阳风等离子体微观状态的长期观测揭示了与观测到的波动的直接相关性，指出了动力学不稳定性对波动的局部产生和放大。低能量（核心）人口接近能量均分，并限制在由动力学不稳定性的阈值形成的温度各向异性的限制。然而，这个难题仍然是未解决的超热人口，虽然他们包括一个显着的动能密度和维持空间等离子体的热平衡，即使在没有动力学各向异性。在拟议的3年项目中，我们将以前所未有的详细程度调查核心和晕人口的相互作用，这似乎是决定性的等离子体波动的产生和演变。主要目标是制定一个现实的预测和表征等离子体波动的动力学各向异性在太阳风的理论基础。这将通过使用广义Kappa分布函数在动力学水平上对各向异性等离子体状态进行建模来实现，广义Kappa分布函数代表了自洽描述太阳风等离子体动力学的先进的强大工具。在线性理论的框架内确定的不稳定条件和最大增长率是特别重要的，并将揭示最快的松弛过程的动力学各向异性。特别注意的是电子和质子的相互作用，因为这些可以显着改变不稳定的条件，和弱传播和非周期性波动，通常被忽略，但似乎比周期性模式更有效。拟议的研究计划包括第一次分析和数值研究的准线性（弱非线性）的各向异性Kappa分布等离子体中的自生microinstabilites的演变。这使得一个全面的研究的线性和非线性演化的波动，包括他们的反作用的速度分布和他们的时刻，即宏观等离子体参数。考虑到目前对非平衡等离子体物理学的普遍兴趣，以及考虑到过去、当代、特别是即将进行的航天器飞行任务提供的大量观测数据为增进我们对这种等离子体的了解提供了机会，这个项目是非常及时的。

Long-term surveys of the solar wind plasma microstates have revealed a direct correlation with observed fluctuations, pointing to a local generation and amplification of the latter by the kinetic instabilities. The low-energy (core) populations are close to an energy equipartition and constrained within the limits of temperature anisotropy shaped by the thresholds of the kinetic instabilities. However, this puzzle is still unresolved for the suprathermal populations, although they comprise a significant kinetic energy density and maintain the space plasmas out of thermal equilibrium even in the absence of kinetic anisotropies. Within the proposed 3-year project we will investigate in unprecedented detail the interplay of the core and halo populations that appears to be decisive in the generation and evolution of plasma fluctuations. The main goal is the formulation of a theoretical basis for a realistic prediction and characterization of plasma fluctuations induced by the kinetic anisotropies in the solar wind. This will be achieved by modeling the anisotropic plasma states on the kinetic level using generalized Kappa distribution functions, which represent an advanced powerful tool to self-consistently describe the solar wind plasma dynamics. The instability conditions and the maximum growth rates determined within the framework of the linear theory are particularly important and will unveil the fastest relaxation process of the kinetic anisotropy. Special attention will be given both to the mutual effects of electrons and protons as these can significantly change the instability conditions, and to the weakly propagating and aperiodic fluctuations which are usually ignored but appear to be more efficient than periodic modes. The proposed research programme comprises the first analytical and numerical investigation of the quasilinear (weakly-nonlinear) evolution of the self-generated microinstabilites in anisotropic Kappa distributed plasmas. This enables a comprehensive study of the linear and nonlinear evolution of fluctuations, including their back reaction on the velocity distributions and on their moments, i.e. on the macroscopic plasma parameters. This project is very timely in view of the present general interest in physics of non-equilibrium plasmas, as well as in view of the opportunities to advance our understanding of such plasmas offered by a large amount of observational data from passed, contemporary and, particularly, of forthcoming spacecraft missions.