The Evolution of Galactic and Intergalactic Magnetic Fields

AST-0507367 Zweibel这个项目将有助于澄清天体物理学的一个基本问题：磁场的起源是什么，它们是如何演变的？ 观测表明，在宇宙还不到现在年龄的十分之一时，星系和星系际介质中就已经存在磁场。 这些场似乎不太可能是在大爆炸中产生的，最近的研究表明，它们是由一个小的“种子”场的产生及其随后的磁流体湍流放大而产生的。 这一想法仍然面临重大的技术困难。 这项研究将考虑高能粒子或宇宙射线与非常弱的磁场的相互作用，从分析和数值上探索能量交换。 它将研究一个复杂的“自举”过程，即流动的宇宙射线放大螺旋波动，增强磁场和加速宇宙射线，放大更多的波动，等等。这项研究还将导致改进星系际介质中宇宙射线加速的理论，包括基于辐射和核合成特征的可测试的预测。该研究将培养至少一名高级计算和跨学科工作的学生在天体物理学和等离子体物理学的交界处。

AST-0507367ZweibelThis project will help to clarify one of the fundamental questions of astrophysics: what is the origin of magnetic fields, and how do they evolve? Observations show that magnetic fields existed in galaxies and in the intergalactic medium by the time the Universe was less than a tenth its present age. It seems unlikely these fields were created in the Big Bang, and recent work suggests they arose by the creation of a small 'seed' field and its subsequent amplification by hydro-magnetic turbulence. This idea still faces significant technical difficulties. This research will consider the interaction of energetic particles, or cosmic rays, with very weak magnetic fields, exploring the exchange of energy both analytically and numerically. It will investigate a conjectured 'bootstrap' process whereby streaming cosmic rays amplify helical fluctuations, growing the magnetic field and accelerating cosmic rays, which amplify more fluctuations, and so on. This study should also lead to an improved theory for cosmic ray acceleration in the intergalactic medium, including testable predictions based on radiative and nucleosynthetic signatures.The research will train at least one student in advanced computing and in interdisciplinary work at the interface between astrophysics and plasma physics.