New Challenges to Astrophysical Particle Acceleration

尽管宇宙射线是在近一个世纪前被发现的，但关于它们在哪里被加速，如何被加速，以及它们是如何传播给我们的细节，仍然有些神秘。加速可能发生在许多宇宙源中，包括自转、磁化的中子星、大质量黑洞、伽马射线爆发、超新星爆炸产生的冲击波，甚至是星系团周围类似但更大的冲击。由于最近的发现，以及对宇宙射线光谱和成分测量的极大改进，该领域正在重新焕发生机。这个项目是对跨越几个地点的宇宙粒子加速机制的理论研究，并对最近的观测做出回应。它将探索被称为单极感应的机制，并详细分析粒子如何在非常小的步骤中获得能量和动量，例如在激波前沿附近。定性地，我们将使用简单的分析和更详细的模拟来研究新类型的磁重联和相对论激波前锋。这些结果应该有助于解释最近对宇宙源的令人惊讶的观测结果，这些观测覆盖了70个八度及以上的电磁频谱。尽管人们关注了一个世纪，但对这些问题只有部分了解，同时通过观测和模拟来解决它们需要相当复杂的工具。这项工作广泛地与太阳天气、磁场和惯性聚变的研究联系在一起，这些都是公众强烈关注和社会关注的话题。学生将接受宝贵的等离子体天体物理学培训，这是为许多其他领域做好准备。

Although cosmic rays were discovered almost a century ago the details of where and how they are accelerated and how they propagate to us remain somewhat mysterious. Acceleration can occur in many cosmic sources, including spinning, magnetized neutron stars, massive black holes, gamma ray bursts, shock waves expanding from supernova explosions, and even similar but larger shocks surrounding clusters of galaxies. The field is being revitalized by recent discoveries, and by greatly improved measurements of the spectra and composition of cosmic rays. This project is a theoretical investigation of cosmic particle acceleration mechanisms spanning several sites and responding to recent observations. It will explore the mechanism known as unipolar induction, and analyze in detail how particles can acquire energy and momentum in very small steps, such as in the vicinity of shock fronts. Qualitatively new types of magnetic reconnection and relativistic shock fronts will be studied using both simple analysis and more detailed simulations. The results should help to explain recent surprising observations of cosmic sources, throughout the seventy octave electromagnetic spectrum and beyond.These problems have been only partially understood despite a century of attention, and tackling them both observationally and through simulation will require quite sophisticated tools. The work links broadly to the study of solar weather, and of magnetic and inertial fusion, topics of strong public interest and societal concern. A student will receive valuable training in plasma astrophysics, which is a good preparation for many other fields.