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Magnetic field phenomenology: from the Universe to laboratory experiments

磁场现象学：从宇宙到实验室实验

基本信息

批准号：
1947611
负责人：
金额：
--
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-1947611
关键词：
Magnetic field phenomenology Universe laboratory

项目摘要

Magnetic fields are an ubiquitous feature of astrophysical and laboratory plasmas, as revealed by diffuse radio-synchrotron emission and Faraday rotation observations. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are embedded, making magnetic fields essential players in the dynamics of the luminous matter. How such fields are created and amplified remains a mystery. It is believed that turbulent dynamo action can efficiently amplify magnetic fields and this is supported by novel laboratory experiments that we have performed in the past few years. Thus the magnetic fields observed in astronomical bodies today could plausibly have arisen from tiny initial seeds. Still, the origin of such seeds remains unclear - and a variety of plasma processes have been proposed, Moreover, such amplification process cannot occur in cosmic voids, where the plasma density is too small for dynamo to become operative.These considerations are part of a more fundamental question of how the energy injected at large scales into a compressible plasma is partitioned, in a turbulent cascade, between small-scale motions, magnetic and compressive fluctuations, and dissipated via cosmic rays. Indeed, the presence of energetic particles in the Universe is a well established fact. The exact mechanism that leads to such high energy particles remains controversial. Although many different processes may result in cosmic ray acceleration, the current understanding is that turbulence and magnetic fields play an essential role in energizing both the electrons and ions present in the interstellar medium.We plan to tackle this problem using a multi-strategy approach that focuses on:1. Developing novel theoretical models for magnetic field generation in the Universe that applies plasma-physics processes (such as returns currents, baroclinic effects and/or turbulent dynamo) and go beyond them (for example, using non-standard model physics). We will investigate processes that occurs in the early Universe as well those that occurs in supernova remnants.2. Embed these models into simulation codes - particularly particle-in cell (OSIRIS and/or EPOCH) and predict measurable quantities that can be tested against observations and laboratory experiment. Examples are the spectrum of the magnetic field, or secondary processes such as photon (x-ray) production.3. Understand the interplay between magnetic field generation, amplification and particle acceleration - for example second order Fermi acceleration - and develop phenomenological models that can be validated with experiments on high-power laser facilities.This project fits "Plasmas and lasers"

磁场是天体物理和实验室等离子体的普遍特征，漫射同步辐射和法拉第旋转观测揭示了这一点。这些磁场的能量密度通常与它们所在的等离子体的流体运动的能量密度相当，这使得磁场在发光物质的动力学中扮演着重要的角色。这些领域是如何被创造和放大的仍然是一个谜。人们相信，湍流的发电机作用可以有效地放大磁场，这一点得到了我们在过去几年中进行的新颖的实验室实验的支持。因此，今天在天文天体中观察到的磁场可能是从微小的初始种子中产生的。尽管如此，这种种子的来源仍然不清楚--而且已经提出了各种等离子体过程，此外，这种放大过程不能在宇宙空洞中发生，因为那里的等离子体密度太小，发电机无法运行。这些考虑是一个更根本问题的一部分，即大规模注入可压缩等离子体的能量如何在湍流级联中在小规模运动、磁力和压缩波动之间分配，并通过宇宙射线消散。事实上，宇宙中高能粒子的存在是一个公认的事实。导致这种高能粒子的确切机制仍然存在争议。虽然许多不同的过程可能导致宇宙线加速，但目前的理解是，湍流和磁场在激发星际介质中的电子和离子方面起着至关重要的作用。我们计划使用多策略方法来解决这个问题，重点是：1.开发新的理论模型，用于宇宙中磁场的产生，应用等离子体物理过程(如返回电流、斜压效应和/或湍流发电机)并超越它们(例如，使用非标准模型物理)。我们将研究发生在早期宇宙中的过程，以及发生在超新星遗迹中的过程。将这些模型嵌入到模拟代码中，特别是粒子-in cell(OSIRIS和/或EPOCH)，并预测可测量的量，这些量可以根据观测和实验室实验进行测试。例如磁场的光谱，或二次过程，如光子(x射线)的产生。了解磁场产生、放大和粒子加速之间的相互作用--例如，二阶费米加速--并开发可用高功率激光设备的实验进行验证的唯象模型。