Understanding particle acceleration in collisionless shocks using kinetic simulations

使用动力学模拟了解无碰撞冲击中的粒子加速度

• 批准号: 1814708
• 负责人: Anatoly Spitkovsky
• 金额: $ 52.66万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-15 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1814708&HistoricalAwards=false
• 关键词: Understanding; particle; acceleration; collisionless; shocks

Collisionless shocks occur in tenuous plasmas where the mean free path for collisions mediated by electrostatic interaction is large, as found in supernova remnants, clusters of galaxies, relativistic jets, and pulsar winds. The conditions under which this occurs, and the efficiency of accelerating charged particles, are not well understood. This project will carry out advanced numerical simulations and use them to construct a self-consistent theory of shock acceleration. It will resolve the complex microphysics of plasma instabilities, particle scattering, and magnetic field generation and amplification, and calibrate the theory for its application to astrophysical objects. The results will help to interpret new studies of high-energy astrophysical and cosmological sources, including the next generation of laboratory experiments, and the physical insights will even apply to shocks in our solar system. The work will train graduate and undergraduate students in numerical modeling and the visualization of multiscale systems, mentor a postdoc, and support open source simulation software and its analysis tools.Collisionless shocks span different speeds and strengths of magnetic field, and accelerate both nonthermal electrons which energize synchrotron emission, and the protons commonly found in cosmic rays. The main process is thought to be diffusive shock acceleration, in which particles scatter on magnetic fluctuations, but the conditions for this Fermi mechanism and its efficiency are not understood from first principles. This project will carry out large-scale multidimensional particle-in-cell (PIC) and hybrid simulations of astrophysical collisionless shocks to consider: 1) what is the relative efficiency of acceleration as a function of shock speed, Mach number, and magnetic inclination? 2) what waves mediate electron acceleration in quasi-parallel and quasi-perpendicular shocks? 3) what is the ratio of electron to ion temperature downstream, and what is the physics of energy transfer? 4) what is the nonlinear structure of the shock when ion acceleration is efficient? With microphysical parameterizations measured with PIC simulations, new software will combine a magneto-hydrodynamic description of the background plasma with kinetic particles to represent cosmic rays and their back-reaction on the flow. This will enable modeling of macroscopic astrophysical objects such as supernova remnants or galactic outflows, including the effects of cosmic rays and their acceleration. These kinetic simulations address how nonlinear shock acceleration works and will constrain the parameters of the flow when it is efficient.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.

无碰撞激波发生在稀薄的等离子体中，那里由静电相互作用介导的碰撞的平均自由程很大，如超新星遗迹，星系团，相对论喷流和脉冲星风。 这种情况发生的条件，以及加速带电粒子的效率，还没有得到很好的理解。 本项目将进行先进的数值模拟，并利用这些模拟来构建冲击加速的自洽理论。 它将解决等离子体不稳定性、粒子散射、磁场产生和放大等复杂的微观物理学问题，并校准理论，以便将其应用于天体物理学目标。 这些结果将有助于解释高能天体物理和宇宙学来源的新研究，包括下一代实验室实验，物理见解甚至将适用于我们太阳系中的冲击。 这项工作将培训研究生和本科生的数值建模和多尺度系统的可视化，指导博士后，并支持开源模拟软件及其分析工具。无碰撞冲击跨越不同的速度和磁场强度，并加速激发同步辐射的非热电子和宇宙射线中常见的质子。 主要的过程被认为是扩散冲击加速，其中粒子在磁场波动中散射，但费米机制的条件及其效率并不从第一原理中理解。 该项目将对天体物理学无碰撞冲击进行大规模多维粒子模拟和混合模拟，以考虑：1）作为冲击速度、马赫数和磁倾角的函数，加速的相对效率是多少？2)在准平行冲击和准垂直冲击中，什么波介导电子加速？3)下游的电子和离子的温度比是多少？能量转移的物理原理是什么？4)当离子加速有效时，激波的非线性结构是什么？ 通过PIC模拟测量的微物理参数，新软件将联合收割机结合背景等离子体的磁流体动力学描述和动力学粒子，以表示宇宙射线及其对流动的反反应。 这将使宏观天体物理对象，如超新星遗迹或银河系外流，包括宇宙射线的影响和加速建模。 这些动力学模拟解决了非线性冲击加速如何工作，并将在有效时约束流的参数。该奖项反映了NSF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。

项目成果

Energy Distribution of Pickup Ions at the Solar Wind Termination Shock

• DOI: 10.3847/1538-4357/aabf96
• 发表时间: 2018-06
• 期刊: The Astrophysical Journal
• 作者: Rahul Kumar;E. Zirnstein;A. Spitkovsky

Electron acceleration in laboratory-produced turbulent collisionless shocks

• DOI: 10.1038/s41567-020-0919-4
• 发表时间: 2020-06-08
• 期刊: NATURE PHYSICS
• 影响因子: 19.6
• 作者: Fiuza, F.;Swadling, G. F.;Park, H-S
• 通讯作者: Park, H-S

Kinetic simulations of mildly relativistic shocks – I. Particle acceleration in high Mach number shocks

• DOI: 10.1093/mnras/stz232
• 发表时间: 2018-09
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: P. Crumley;D. Caprioli;S. Markoff;A. Spitkovsky

Kinetic Simulations of Electron Pre-energization by Magnetized Collisionless Shocks in Expanding Laboratory Plasmas

膨胀实验室等离子体中磁化无碰撞冲击电子预激励的动力学模拟

• DOI: 10.3847/2041-8213/abe407
• 发表时间: 2021
• 期刊: The Astrophysical Journal
• 作者: Lezhnin, K. V.;Fox, W.;Schaeffer, D. B.;Spitkovsky, A.;Matteucci, J.;Bhattacharjee, A.;Germaschewski, K.
• 通讯作者: Germaschewski, K.

Electron Injection via Modified Diffusive Shock Acceleration in High-Mach-number Collisionless Shocks

在高马赫数无碰撞激波中通过改进的扩散激波加速进行电子注入

• DOI: 10.3847/2041-8213/ad0cf9
• 发表时间: 2023
• 期刊: The Astrophysical Journal Letters
• 作者: Grassi, A.;Rinderknecht, H. G.;Swadling, G. F.;Higginson, D. P.;Park, H.-S.;Spitkovsky, A.;Fiuza, F.
• 通讯作者: Fiuza, F.