Dynamics of Strongly Coupled Complex Plasma Systems with Directed Ion Flow

这个研究项目将调查尾流，这是一种在自然界中广泛遇到的现象，跨越了一系列的长度尺度。在中子星加速穿过星际气体时的弓形激波中，在空气流过海洋岛屿时的云状图案中，以及在流动的溪流中的岩石后面，都可以观察到尾迹。骑自行车的人利用队友产生的尾流，紧挨着彼此骑行以节省能量。本文研究了复杂等离子体中带正电荷的离子流过带负电荷的尘埃粒子所形成的尾迹。复杂等离子体中微米大小的尘埃粒子具有自组织成各种各样结构的能力。就像吸引骑自行车的人一样，被困在流动的等离子体中的尘埃颗粒往往会在彼此的下游排成一行。尾流场粉尘排列所带来的能量节约对粉尘结构的动力学和稳定性有影响。复杂等离子体是研究结构形成等动态效应的一个极好的系统，因为它们允许在容易接近的空间和时间尺度上进行直接观察。对复杂等离子体中振荡模式和结构跃迁的研究也可以为其他有限系统的动力学提供见解，这些系统不容易成像。许多尘埃等离子体实验利用悬浮在等离子体和边界表面之间形成的护套中的尘埃颗粒。鞘中存在的电场加速等离子体离子向边界面移动，导致颗粒下游的离子尾流。本研究的主要目的是研究等离子体尾流场相互作用对复杂等离子体环境中自组装尘埃结构的自组织、动力学和相变的影响。这项研究结合了计算技术和实验技术。动态计算模拟是必要的，因为力、电荷和尾迹都随着粒子的位置和其他粒子的接近而变化。数值模型将提供离子流中尘埃颗粒的动力学、电荷和各向异性筛选的自一致计算。充电和尾流场的形成将与等离子体环境联系起来，定义等离子体对边界条件的响应。同时，还需要实验技术，以可控的方式产生特定的粒子结构。实验室实验将采用最先进的技术来控制和限制尘埃在具有明确特征的尘云、弦、团和晶体内。在实验上，尘埃颗粒也将被用作原位探针来测量局部等离子体环境，为数值模型提供数据。

This research project will investigate wakes, a phenomenon widely encountered in nature and spanning a range of length scales. Wakes are observed in the bow shock of a neutron star speeding through interstellar gas, in cloud patterns as air flows past ocean islands, and behind rocks in flowing streams. Cyclists take advantage of the wake created by their teammates, riding close behind each other to conserve energy. This research investigates the wakes formed by positively charged ions flowing past negatively charged dust particles in a complex plasma. The micron-sized dust particles in a complex (dusty) plasma have the ability to self-organize into a wide variety of structures. Much like drafting cyclists, dust particles trapped in the flowing plasma tend to line up downstream of each other. The energy savings due to dust alignment in the wakefield has an effect on the dynamics and the stability of dust structures. Complex plasmas are an excellent system for studying dynamic effects such as structure formation, as they allow direct observation at easily accessible space and time scales. An investigation of the modes of oscillation and structural transitions in a complex plasma can also provide insight into the dynamics of other finite systems which cannot be easily imaged.Many dusty plasma experiments utilize dust grains suspended in the sheath formed between the plasma and a bounding surface. The electric fields present in the sheath accelerate the plasma ions towards the bounding surface, leading to an ion wake downstream of the grains. The primary objective of this research is to investigate the effect of the plasma wakefield interaction on the self-organization, dynamics, and phase transitions in self-assembled dust structures within a complex plasma environment. This research merges computational and experimental techniques. A dynamic computational simulation is needed, as forces, charges, and wakes all change with particle location and the proximity of other particles. Numerical models will provide self-consistent calculations of dynamics, charging and anisotropic screening of dust particles in an ion flow. Charging and wakefield formation will be linked to the plasma environment, defining the response of the plasma to boundary conditions. At the same time, experimental techniques are needed that can produce specific particle structures in a controlled manner. Laboratory experiments will employ state-of-the-art techniques designed to control and confine the dust within dust clouds, strings, clusters, and crystals with defined characteristics. Experimentally, dust particles will also be used as in situ probes to measure the local plasma environment providing data for use in the numerical models.