Quasilinear Dissipation of Turbulently-Generated Kinetic Alfven Waves: Kinetics of Ion Heating and Solar Wind Acceleration in Coronal Holes

太阳风定义了地球的等离子体环境，调解了所有的太阳扰动和空间天气影响。对流动过程的全面微观理解将有助于这些领域的研究。这项为期3年的关于湍流产生的动力学阿尔芬波（KAWs）对离子加热的研究将解决长期存在的难题，即太阳风是如何通过阿尔芬等离子体湍流的耗散而加热和加速的。从这一机制中预期的离子能量应该最终为详细的太阳风模型提供动力学基础，这些模型需要精确的、物理驱动的加热速率。它还将为太阳风中重离子的优先加热提供物理解释。最终，这个为期3年的项目将产生一个多离子加速和加热太阳风从日冕洞出来时的定量动力学模型。此外，它将为等离子宇宙中涉及湍流的许多其他现象提供有价值的见解，例如太阳和恒星耀斑，超新星遗迹，致密物体的吸积盘，以及星际，星系间和星团内的流动。此外，项目团队成员积极参与联合国大学的教育工作，这笔拨款提供的支持将使他们能够继续与研究生和本科生进行富有成效的研究互动。人们普遍认为太阳风是由日冕等离子体湍流耗散引起的离子加热驱动的。这个加热过程的动力学细节决定了所产生的风的微观特性，但这些细节目前尚不清楚。从观测上看，加热必须优先作用于垂直离子运动，并且对重离子的作用比对质子的作用更强。等离子体湍流的模拟可以产生这些结果，但不能清楚地指出动力学机制。最近，一幅无碰撞湍流的图像出现了，它描述了kaw方面的小尺度波动。这些波动是高度倾斜的、压缩的和椭圆极化的。虽然这些湍流起伏不是标准意义上的波，但它们的极化和传播特性仍然可以从等离子体色散关系中得到。过去，该项目团队已经证明，kaw的一个看似合理的湍流谱将通过拟线性（QL）回旋共振在垂直方向上加热离子，并且这种加热可以在与太阳风相关的情况下主导看似更强的朗道共振的效果。在这个为期3年的项目中，该团队将对日冕和太阳风中的QL相互作用进行彻底的研究，在他们最初的例子中添加更多的物理细节，并研究不同等离子体和湍流特性的影响。在每种情况下，研究小组将遵循从我们的任意线性等离子体求解器（ALPS）获得的离子分布和波动色散关系的自一致演变。研究人员将探索不同等离子体β的影响：对湍流光谱形状的不同假设；不平衡湍流谱；间歇性;共振展宽。他们将在这些探索中研究重离子的优先效应。空间均匀研究的结果将被纳入他们的非均匀动能导向中心日冕洞模型，该模型推导出湍流加热与全球日冕力耦合时径向依赖的离子分布。该项目的研究和EPO议程支持AGS部门在发现、学习、多样性和跨学科研究方面的战略目标。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The solar wind defines the Earth's plasma environment, mediating all solar disturbances and space weather effects. A full microscale understanding of the processes that operate in the flow will aid investigations in these areas. This 3-year research study of ion heating by turbulently generated kinetic Alfven waves (KAWs) will address the long-standing puzzle of how the solar wind is heated and accelerated through the dissipation of Alfvenic plasma turbulence. The ion energization expected from this mechanism should finally provide a kinetic basis for detailed solar wind models that require accurate, physically motivated heating rates. It will also provide a physical explanation for the preferential heating of heavy ions in the solar wind. Ultimately, this 3-year project will yield a quantitative kinetic model of the multi-ion accelerated and heated solar wind as it emerges from a coronal hole. Furthermore, it will provide valuable insight on the many other phenomena in the plasma universe that involve turbulence, such as solar and stellar flares, supernova remnants, accretion discs of compact objects, as well as interstellar, intergalactic and intra-cluster flows. Additionally, the project team members are active participants in the educational efforts at the UNH, and the support provided by this grant will enable continuation of their productive research interactions with graduate and undergraduate students.It is widely accepted that the solar wind is driven by ion heating due to the dissipation of plasma turbulence in the solar corona. The kinetic details of this heating process determine the microscale properties of the resulting wind, but such details are not presently known. Observationally, the heating must act preferentially on the perpendicular ion motion, and act more strongly on heavy ions than on protons. Simulations of plasma turbulence can produce these results but do not clearly pinpoint the kinetic mechanism. Recently, a picture of collisionless turbulence has emerged that describes the small-scale fluctuations in terms of KAWs. These fluctuations are highly oblique, compressive, and elliptically polarized. Although these turbulent fluctuations are not waves in the standard sense, their polarization and propagation properties may still be obtained from a plasma dispersion relation. In the past, the project team has shown that a plausible turbulent spectrum of KAWs will heat ions in the perpendicular direction through the quasilinear (QL) cyclotron resonance, and that this heating can dominate the effect of the seemingly stronger Landau resonance in circumstances relevant to the solar wind. During this 3-year project, the team will carry out a thorough investigation of this QL interaction in the corona and solar wind, adding more physical details to their initial example and investigating the effects of different plasma and turbulent properties. In each case, the team will follow the self-consistent evolution of the ion distributions and fluctuation dispersion relations obtained from our Arbitrary Linear Plasma Solver (ALPS). The investigators will explore the effects of different plasma beta: different assumptions on the turbulent spectral shape; imbalanced turbulent spectra; intermittency; and, resonance broadening. They will study the preferential effects on heavy ions throughout these explorations. The results of spatially homogeneous studies will be incorporated into their inhomogeneous kinetic guiding-center coronal hole model, which derives radially dependent ion distributions when the turbulent heating is coupled with global coronal forces. The research and EPO agenda of this project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.