Charged particel transport in interstellar plasmas: Improved theory for scattering of cosmic rays in turbulent fields

星际等离子体中的带电粒子输运：湍流场中宇宙射线散射的改进理论

• 批准号: 203247539
• 负责人: Professor Dr. Frank Jenko
• 金额: --
• 依托单位: Institut für Theoretische Physik IV: Weltraum- und Astrophysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2011
• 资助国家: 德国
• 起止时间: 2010-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/203247539?language=en
• 关键词: Charged; particel; transport; interstellar; plasmas

Cosmic rays, charged dust particles and turbulent magnetic fields are important constituents of the interstellar medium. Understanding and predicting the transport of charged particles in turbulent media is a key challenge in a number of related disciplines, ranging from magnetic confinement fusion research to astrophysics. In astrophysics, it is the scattering, acceleration and spatial diffusion of cosmic rays in interstellar magnetic fields. The purpose of this proposal is two-fold:First, we want to investigate the transport of fast particles in cosmic magnetic fields, applying scaling concepts which were developed recently in the context of tokamak physics based on the percolation theory. This can be done since although the turbulent scales are extremely different, the scattering mechanisms perpendicular to the background field are basically the same.Secondly, we want to develop an improved weak turbulence transport theory of fast charged particles in a partially turbulent magnetic field, that avoids the usually made quasilinear approximation to the particle orbits, and properly takes into account recent nonlinear improvements. Three statistical properties of the magnetic turbulence are adopted: (1) quasi-stationary turbulence, (2) the existence of a finite turbulence decorrelation time, and (3) spatially homogenous turbulence. In contrast to the scaling theory, weak turbulence transport theories often make use of the Corrsin independence hypothesis allowing one to express a fourth order correlation function in terms of the product of two second order correlation functions. Two central goals of this proposal are (1) the calculation of cosmic ray scattering rates from weak turbulence and scaling transport theories, respectively, and (2) their comparison to verify or disprove the validity of the Corrsin hypothesis for cosmic turbulent magnetic fields. The so improved transport theory will be applied to selected interstellar phenomena such as the diffusive shock acceleration of cosmic ray particles in the presence of large scale parallel spatial gradients of the guide magnetic field.

宇宙射线、带电尘埃粒子和湍流磁场是星际介质的重要组成部分。理解和预测带电粒子在湍流介质中的传输是许多相关学科（从磁约束聚变研究到天体物理学）的关键挑战。在天体物理学中，它是宇宙射线在星际磁场中的散射、加速和空间扩散。该提案的目的有两个：首先，我们希望应用最近在托卡马克物理背景下基于渗流理论发展起来的尺度概念，研究宇宙磁场中快速粒子的传输。这是可以做到的，因为尽管湍流尺度截然不同，但垂直于背景场的散射机制基本相同。其次，我们希望发展一种改进的部分湍流磁场中快带电粒子的弱湍流输运理论，避免通常对粒子轨道进行的拟线性近似，并适当考虑最近的非线性改进。采用磁湍流的三个统计特性：（1）准稳态湍流，（2）有限湍流去相关时间的存在，以及（3）空间均匀湍流。与标度理论相反，弱湍流传递理论经常利用 Corrsin 独立假设，允许人们用两个二阶相关函数的乘积来表达四阶相关函数。该提案的两个中心目标是（1）分别根据弱湍流理论和尺度输运理论计算宇宙射线散射率，以及（2）通过比较它们来验证或反驳宇宙湍流磁场的科森假说的有效性。如此改进的输运理论将应用于选定的星际现象，例如在引导磁场的大规模平行空间梯度存在的情况下宇宙射线粒子的扩散冲击加速。