Energy Transfer in Collisionless Astrophysical Plasmas

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。本研究聚焦于等离子体物理学的两个前沿领域，其中粒子胞内（PIC）模拟可以帮助阐明等离子体中能量传递的基本原理：(1)在无碰撞吸积盘的激励下，我们将研究在离子温度远高于电子温度的各向异性双温等离子体中，离子和电子之间是否会发生比库仑更快的能量传递。将考虑由大块剪切流、Weibel、双流和其他无碰撞MHD不稳定性产生的波的电子-质子耦合。存在或不存在比柱体更快的耦合将严格限制双温度吸积流的可行性，例如平流主导的吸积流作为一些星系核的辐射低效吸积流的范例，以及x射线双星的状态。(2)基于电流驱动的weibel型不稳定性在天体物理驱动冲击和激光驱动冲击中的基本作用，研究人员将对两种类型的形成和磁场产生进行研究和比较。本科生将参与数据分析和可视化。将扩大对罗切斯特大学正在进行的本科生广播节目的支持。该节目每两周播出一次，重点介绍一些科学和工程方面的发展，但会重复播出3-4分钟，向罗切斯特地区播出。大学正在为物理学、天体物理学和工程学的研究生和本科生开设一门关于PIC模拟的课程。关于PIC的讲座也将在由美国能源部聚变科学中心组织的暑期学校进行。该项目将产生新的教材，以展示PIC模拟如何应用于新的研究领域。该项目还将培养具有等离子体物理学、天体物理学和PIC模拟跨学科专业知识的研究生和博士后研究人员。该提案已提交给NSF-DoE等离子体科学与工程合作项目联合招标08-589。该奖项由数学和物理科学理事会的物理和天文科学部联合资助。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This research focuses on two frontiers of plasma physics where particle-in-cell (PIC) simulations can help elucidate underlying principles of energy transfer in plasmas: (1) Motivated by collisionless accretion disks, we will study whether a faster-than-Coulomb energy transfer between ions and electrons can occur in a two-temperature plasma with an anisotropic ion temperature much higher than the electron temperature. Electron-proton coupling via waves generated by bulk sheared flows, Weibel, two-stream, and other collisionless MHD instabilities will be considered. The presence or absence of a faster-than-Columb coupling will place rigorous constraints on the viability of two-temperature accretion flows such as advection dominated accretion flows as a paradigm for the radiatively inefficient accretion flows of some galactic nuclei, and states of X-ray binaries. (2) Motivated by the fundamental role of the current-driven Weibel-type instabilities in both astrophysically motivated shocks and laser-driven shocks, researchers will study and compare the formation and magnetic field generation in both types. Undergraduates will be involved in the data analysis and visualization. Support for an ongoing undergraduate radio show at the University of Rochester will be expanded. The show highlights a few science and engineering developments biweekly for a short, but repeated 3-4 minute broadcasts to the Rochester area. A course on PIC simulations is being developed at UR for graduate and undergraduate students from physics, astrophysics, and engineering. Lectures on PIC will also be given at the Summer Schools organized by the UR DOE Fusion Science Center. This project will generate new teaching materials to demonstrate how PIC simulations can be applied to new research areas. The project will also train graduate students and postdoctoral researchers with interdisciplinary expertise in plasma physics, astrophysics, and PIC simulations.This proposal was submitted to the NSF-DoE Partnership in Plasma Science and Engineering joint solicitation 08-589. This award is being funded jointly by the Divisions of Physics and Astronomical Sciences of the Mathematical and Physical Sciences Directorate.