报告题目：扩散激波加速机制的蒙特卡洛模拟

报 告 人：王新(国家天文台)

摘　  要：“扩散激波加速理论是宇宙线物理中重要的加速机制。它涵括了太阳高能粒子，银河系内甚高能粒子，乃至宇宙中超高能粒子的起源和加速机制问题。太阳高能粒子因其影响日地空间环境乃至人类的生存环境，日益被人们重视和关注。该研究拟就扩散激波在太阳物理中关于高能粒子的起源和演化的作用做进一步的探讨，探讨高能粒子在行星系际激波，地球弓激波，以及在太阳耀斑和日冕物质抛射活动中的产生和演化的行为。为揭示在激波的非线性过程中产生高能粒子的机制，该研究选用了蒙特卡洛模拟方法来模拟太阳风流形成激波并产生高能粒子的演化过程。得到了激波非线性过程中产生的粒子的非热幂律谱分布。验证了一阶费米加速过程在太阳高能粒子产生中的重要作用。在模拟方法上，该研究还提出了在可压缩流体激波中应用各向异性的高斯散射角分布的散射机制。通过对不同的标准差值的高斯型散射角分布函数对应的事例进行模拟，总结出了扩散激波加速机制产生的粒子能谱与所采用的基于各向异性散射角分布函数的散射律之间的规律。

关 键 词：扩散激波加速、费米加速、宇宙线、耀斑、日冕物质抛射、粒子模拟

报告时间：2012年8月13日（周一）12:00

报告地点：紫台大楼517会议室

联 系 人：刘四明（83332173）

欢迎大家积极参加！

　　　　　　　　　　　　　　　　　 紫金山天文台学术委员会学术交流工作委员会

Title：Monte Carlo Simulations of A Diffusive Shock Acceleration

Xin Wang NAOC.

Abstract: Diffusive shock acceleration theory is an important acceleration mechanism in the cosmic ray physics. It includes the productions and the acceleration mechanism of the solar energetic particles, Galactic very high energy cosmic ray, and the ultra high energy cosmic ray in the early universe. The aim of this study is to further research the capability, which the diffusive shock acceleration will play an important role in the production and evolution of the solar energetic particles, in the solar physics. Specifically, these discussions are include the productions and evolutions of the energetic particles in the interplanetary shock, Earth bow shock, and the solar flare as well as coronal mass ejections (CME). In order to exhibit the nonlinear interaction between the particles and shock waves, Monte Carlo method adopt in this research is used to simulate the total processes of the formation of the shock by the compression of solar wind flow and the energetic particles' productions. And the "power law" of the accelerated particles distribution produced in the shock downstream regions are presented. Simultaneously, the First-order Fermi acceleration mechanism is verified for playing a major role in the diffusive shock processes in solar physics. This research also proposes that an anisotropic Gaussian scattering angular distribution is capable to be used in the compression fluid shock. By simulating the cases applying different Gaussian scattering angular distributions, the results validate that the particles energy spectrum is greatly dependent on the multiple scattering angular distribution laws.

Keywords: diffusive shock acceleration, Fermi acceleration, cosmic ray, flare,CME, particles simulation