Electron energization at oblique SNR shocks in turbulent media

湍流介质中倾斜 SNR 冲击下的电子赋能

• 批准号: 525227961
• 负责人: Professor Dr. Martin Karl Wilhelm Pohl
• 金额: --
• 依托单位: Institut für Physik und Astronomie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/525227961?language=en
• 关键词: Electron; energization; oblique; SNR; shocks

Where and how cosmic rays are produced in the Galaxy is an important question in modern physics. Observations of nonthermal X-rays and high-energy gamma-rays from shell-type supernova remnants (SNR) imply that nonrelativistic collisionless shocks can efficiently accelerate charged particles. Diffusive shock acceleration is a likely process for the acceleration to very high energies, but requires a preacceleration of electrons to about 50 MeV for SNR shocks. We conduct extensive particle-in-cell (PIC) simulations of collisionless shocks to investigate the processes of electron acceleration and heating at shocks. Building on earlier simulations of collisionless shocks in homogeneous environments, we now propose to study the impact of pre-existing fluctuations in the upstream medium. We know from measurements in the heliosphere that such fluctuations exist and expect that they do so also in the environment of SNRs. We also know that fluctuations on large scales can drive magnetic field amplification at, and induce rippling of, the shocks. Here we are interested in the effect of turbulence on small scales. We shall investigate the effect of pre-existing turbulence on the electron dynamics and on the driving and saturation of plasma waves. If pre-existing turbulence enhances the efficiency of electron energization, it would indicate an answer to the question of electron injection. This long-standing unsolved problem is crucially important to our understanding of particle acceleration at shocks.

宇宙射线在银河系中是在哪里以及如何产生的，这是现代物理学中的一个重要问题。对壳型超新星遗迹(SNR)的非热X射线和高能伽马射线的观测表明，非相对论无碰撞激波可以有效地加速带电粒子。扩散激波加速是加速到很高能量的可能过程，但对于SNR冲击，需要电子预加速度到约50 MeV。我们对无碰撞激波进行了大量的粒子单元(PIC)模拟，以研究激波中电子加速和加热的过程。基于早先对均匀环境中无碰撞冲击的模拟，我们现在建议研究上游介质中预先存在的波动的影响。我们从日光层的测量中了解到，这种波动是存在的，并预计它们在SNR的环境中也是如此。我们还知道，大尺度的波动可以在冲击时驱动磁场放大，并引发涟漪。这里我们感兴趣的是小尺度上的湍流效应。我们将研究预先存在的湍流对电子动力学的影响以及对等离子体波的驱动和饱和的影响。如果先前存在的湍流提高了电子能量的效率，这将预示着电子注入问题的答案。这个长期悬而未决的问题对我们理解激波中的粒子加速至关重要。