The Maximum Energy of Shock-accelerated Cosmic Rays

IF 4.8 2区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS
Rebecca Diesing
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引用次数: 0

Abstract

Abstract Identifying the accelerators of Galactic cosmic ray (CR) protons with energies up to a few PeV (10 15 eV) remains a theoretical and observational challenge. Supernova remnants (SNRs) represent strong candidates because they provide sufficient energetics to reproduce the CR flux observed at Earth. However, it remains unclear whether they can accelerate particles to PeV energies, particularly after the very early stages of their evolution. This uncertainty has prompted searches for other source classes and necessitates comprehensive theoretical modeling of the maximum proton energy, E max , accelerated by an arbitrary shock. While analytic estimates of E max have been put forward in the literature, they do not fully account for the complex interplay between particle acceleration, magnetic field amplification, and shock evolution. This paper uses a multizone, semianalytic model of particle acceleration based on kinetic simulations to place constraints on E max for a wide range of astrophysical shocks. In particular, we develop relationships between E max , shock velocity, size, and ambient medium. We find that SNRs can only accelerate PeV particles under a select set of circumstances, namely, if the shock velocity exceeds ∼10 4 km s −1 and escaping particles drive magnetic field amplification. However, older and slower SNRs may still produce observational signatures of PeV particles due to populations accelerated when the shock was younger. Our results serve as a reference for modelers seeking to quickly produce a self-consistent estimate of the maximum energy accelerated by an arbitrary astrophysical shock. 1 1 Presented as a thesis to the Department of Astronomy and Astrophysics, The University of Chicago, in partial fulfillment of the requirements for a Ph.D. degree.
冲击波加速宇宙射线的最大能量
识别能量高达几PeV (10 - 15 eV)的银河宇宙射线(CR)质子的加速器仍然是一个理论和观测上的挑战。超新星遗迹(SNRs)是强有力的候选者,因为它们提供了足够的能量来重现在地球上观测到的CR通量。然而,目前还不清楚它们是否能将粒子加速到PeV能量,特别是在它们进化的早期阶段之后。这种不确定性促使人们寻找其他类型的源,并且需要对由任意激波加速的最大质子能量emax进行全面的理论建模。虽然在文献中已经提出了E max的分析估计,但它们并没有完全考虑粒子加速度、磁场放大和激波演化之间复杂的相互作用。本文采用基于动力学模拟的粒子加速度多区半解析模型,对大范围天体物理冲击的E max进行了约束。特别地,我们发展了E max,冲击速度,大小和环境介质之间的关系。我们发现信噪比只能在一组特定的情况下加速PeV粒子,即当激波速度超过~ 104 km s−1并且逃逸粒子驱动磁场放大时。然而,较老和较慢的信噪比仍可能产生PeV粒子的观测特征,因为在较年轻的激波中种群加速。我们的结果为寻求快速产生由任意天体物理冲击加速的最大能量的自一致估计的建模者提供了参考。以论文形式提交给芝加哥大学天文学和天体物理系,部分满足博士学位的要求。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Astrophysical Journal
Astrophysical Journal 地学天文-天文与天体物理
CiteScore
8.40
自引率
30.60%
发文量
2854
审稿时长
1 months
期刊介绍: The Astrophysical Journal is the foremost research journal in the world devoted to recent developments, discoveries, and theories in astronomy and astrophysics.
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