Using Kinetic Entropy to Understand Dissipation in Reconnection and Turbulence

这个项目将有助于详细了解一种叫做磁重联的神秘等离子体过程，这是太空爆炸事件背后的一个过程，包括太阳耀斑和驱动太空天气的所谓地磁风暴。它发生在磁场嵌入过热（电离）气体（等离子体）改变方向并迅速向等离子体释放大量能量的地方。该项目还将有助于理解等离子体湍流，在大尺度注入的能量级联到小耗散尺度。这个项目将寻求一种系统的方法来确定等离子体中耗散发生的位置。方法是开发工具来应用熵的概念，自19世纪后期以来，它一直没有得到充分利用的现代问题。这个项目有能力真正改变地球空间科学领域，因为它将提供使用熵作为耗散诊断的基础设施，这在该领域的许多子领域应该是有用的，并将直接与现有的卫星测量相比较。它通过研究生和博士后研究员的支持来促进教育。目标是首次使用动能熵作为重联和湍流耗散的诊断方法进行系统研究，并将结果与磁层多尺度空间任务的观测数据进行比较。研究小组最近开发了用于颗粒胞内（PIC）码的动力学诊断，因此新的诊断将用于评估无碰撞PIC码的数值耗散，并将其实现到自一致包含耗散的碰撞PIC码中。将两者进行比较，以深入了解耗散发生的位置以及导致耗散的物理机制。根据需要，结果将直接与洛斯阿拉莫斯国家实验室的一位合作者最近开发的新的弗拉索夫-麦克斯韦求解器进行比较。模拟研究将在磁重联和湍流的标准测试问题上进行。这项工作的预期贡献将是研究几乎无碰撞系统耗散的系统方法，可广泛用于等离子体科学，以及对重连和湍流中导致不可逆耗散的原因的新认识。该项目作为美国国家科学基金会/美国能源部基础等离子体科学与工程伙伴关系的一部分得到了支持，由能源部聚变能源科学办公室支持的空间科学研究所共同努力。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。

This project will contribute to a detailed understanding of a mysterious plasma process called magnetic reconnection, a process behind explosive events in space including solar flares and so-called geomagnetic storms that drive space weather. It occurs where a magnetic field embedded in a superheated (ionized) gas, a plasma, changes directions and rapidly releases large amounts of energy into the plasma. The project will also contribute to understanding of plasma turbulence, where energy injected at large scales cascades down to small dissipation scales. This project will pursue a systematic approach to determining where dissipation occurs in plasmas. The approach is to develop the tools to apply the concept of entropy, known since the late 19th century, to this modern problem where it has been underutilized. This project has the capability to be truly transformative to the field of geospace sciences since it will provide the infrastructure for using entropy as a diagnostic for dissipation which should be useful in many subareas of this field, and will be directly comparable to existing satellite measurements. It fosters education through the support of a graduate student and a postdoctoral researcher.The goal is to perform the first systematic study using kinetic entropy as a diagnostic for dissipation in reconnection and turbulence, and to compare the results with observational data from the Magnetospheric Multiscale space mission. The kinetic diagnostic was recently developed for particle-in-cell (PIC) codes by the research team, so the new diagnostic will be used to assess the numerical dissipation in collisionless PIC codes and implemented into a collisional PIC code that self-consistently contains dissipation. The two will be compared to provide strong insights into where dissipation occurs and what physical mechanism causes it. As needed, the results will be compared directly with a new Vlasov-Maxwell solver that was recently developed by a collaborator at the Los Alamos National Laboratory. The simulation study will be carried out on standard test problems in magnetic reconnection and turbulence. The expected contribution of this work will be a systematic approach to study dissipation in nearly collisionless systems which can broadly be used for plasma science, and a newfound understanding of what causes irreversible dissipation in reconnection and turbulence. This project is being supported as a part of the NSF/DOE Partnership in Basic Plasma Science and Engineering, with a collaborating effort at the Space Science Institute supported by the Department of Energy, Office of Fusion Energy Sciences.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.