论文标题
Tycho的超新星残留物中的随机重新加速和磁场阻尼
Stochastic re-acceleration and magnetic-field damping in Tycho's supernova remnant
论文作者
论文摘要
许多研究表明，需要使用粒子反馈和非常有效的磁场扩增与Alfvénic漂移相结合的冲击加速度来解释相当柔软的无线电光谱和Tycho SNR观察到的狭窄边缘。我们表明，当考虑到随机加速度作为次要过程时，Tycho SNR的宽带光谱也可以很好地解释。湍流区域中颗粒的重新加速立即在冲击下方的下游应足够有效，以在能量数十年内影响粒子光谱。在这种情况下，不需要所谓的alfvénic漂移和冲击结构的粒子反馈。此外，我们研究了同步加速器损耗或磁场阻尼在非热丝的形成中起着更为重要的作用。我们使用SNR等离子体流的流体动力模拟在测试粒子模式下求解了完整的粒子传输方程。根据所考虑的模型，根据感应方程计算背景磁场，或者遵循分析曲线。下游区域中的快速模板波提供了颗粒在动量空间中的扩散。我们表明，如果考虑到颗粒的磁场阻尼和随机重新加速，可以很好地解释Tycho的宽带光谱。尽管不如标准DSA高效，但随机加速度在粒子光谱上留下了其烙印，这在无线电波长的发射中尤其明显。我们发现震动后磁场强度$ \ sim330 \，\ mathrm {μg} $的下限，即使对于磁场阻尼场景，也意味着有效的放大。对于无线电范围内的细丝形成，磁场阻尼是必要的，而X射线丝是由同步加速器损耗和磁场阻尼构成的。
A number of studies suggest that shock acceleration with particle feedback and very efficient magnetic-field amplification combined with Alfvénic drift are needed to explain the rather soft radio spectrum and the narrow rims observed for Tycho's SNR. We show that the broadband spectrum of Tycho's SNR can alternatively be well explained when accounting for stochastic acceleration as a secondary process. The re-acceleration of particles in the turbulent region immediately downstream of the shock should be efficient enough to impact particle spectra over several decades in energy. The so-called Alfvénic drift and particle feedback on the shock structure are not required in this scenario. Additionally, we investigate whether synchrotron losses or magnetic-field damping play a more profound role in the formation of the non-thermal filaments. We solve the full particle transport equation in test-particle mode using hydrodynamic simulations of the SNR plasma flow. The background magnetic field is either computed from the induction equation or follows analytic profiles, depending on the model considered. Fast-mode waves in the downstream region provide the diffusion of particles in momentum space. We show that the broadband spectrum of Tycho can be well explained if magnetic-field damping and stochastic re-acceleration of particles are taken into account. Although not as efficient as standard DSA, stochastic acceleration leaves its imprint on the particle spectra, which is especially notable in the emission at radio wavelengths. We find a lower limit for the post-shock magnetic-field strength $\sim330\,\mathrm{μG}$, implying efficient amplification even for the magnetic-field damping scenario. For the formation of the filaments in the radio range magnetic-field damping is necessary, while the X-ray filaments are shaped by both the synchrotron losses and magnetic-field damping.
