星际介质与天体相互作用的实验室天体物理研究

发布时间：2018-06-20 09:53

本文选题：实验室天体物理 + 激光与物质相互作用　；参考：《中国科学院大学(中国科学院物理研究所)》2017年博士论文

【摘要】：实验室天体物理学是强激光科学与天体物理学的交叉前沿学科,利用强激光等实验手段,可以在实验室中创造出类似天体环境的极端物理条件,从而对天体物理过程、机制进行全面、深入、可控的研究。利用强激光与物质相互作用进行的实验室天体物理研究已为理解多种天体物理问题做出了贡献。本论文主要针对宇宙中普遍发生的星际介质和天体相互作用过程,利用高功率激光实验和理论模拟,深入研究了其中的物理机制和相关现象。首先,我们利用高功率激光照射CH平面靶后产生的等离子体撞击柱状障碍物的方法,进行了弓激波实验,生成了高马赫数的弓激波。通过阴影和干涉成像诊断,成功观测到了弓激波的形成及演化。在1 ns延迟时刻,等离子云的马赫数约为15,随着时间推移,等离子体流的马赫数降低,导致了弓激波张角和形状的变化。此外,我们在实验中探测到弓激波的宽度约为50μm,这与离子间的平均碰撞自由程相当,该结果证明了该弓激波的形成机制主要是离子间的碰撞效应。我们采用二维USIM流体程序,模拟了等离子体云和障碍物相互撞击的过程,模拟结果很好地再现了实验结果。其次,利用高功率激光照射固体靶产生的等离子体,模拟了太阳风和彗星相互作用的过程。通过阴影和干涉成像诊断,成功地观测到了障碍物后产生了具有断裂结构的等离子体尾。通过粒子程序模拟,我们发现撞击后的等离子体中,离子和电子间巨大的热速度差异,使障碍物后方产生了电场,电场吸引离子向中间汇聚,导致中间等离子体密度增加形成尾巴,并在尾巴前端出现密度跳变结构。该结果揭示了导致彗星断尾事件的又一可能原因。最后,我们利用强激光照射金属丝靶,获得了围绕金属丝的环形强磁场,利用B-dot探头对磁场的强度进行了测量,并通过模拟,计算出了磁场的空间分布;又利用强激光与CH平面靶相互作用产生的超音速等离子体撞击该金属丝的方法,研究了磁场对弓激波的作用,实验中观察到了磁场的存在对弓激波的影响;同时,通过实验室天体物理定标率的变换,证明了激光照射CH靶产生的强x射线所离化的金属丝等离子体,可以被用来模拟太阳风等离子体。
[Abstract]:Laboratory astrophysics is an interdisciplinary frontier subject of intense laser science and astrophysics. By means of experiments such as intense laser, extreme physical conditions similar to the celestial environment can be created in the laboratory, and thus the astrophysical process can be studied. The mechanism is studied comprehensively, deeply and controllably. The study of laboratory astrophysics by means of the interaction of intense laser and matter has contributed to the understanding of many kinds of astrophysical problems. In this paper, the physical mechanism and related phenomena of the interstellar medium and celestial bodies are studied by means of high-power laser experiments and theoretical simulations. Firstly, by using the method of the plasma impingement on the cylindrical obstacle produced by the high power laser irradiation on the Ch plane target, the bow shock wave with high Mach number is generated. The formation and evolution of bow shock waves were observed successfully by shadow and interference imaging diagnosis. At 1 ns delay time, the Mach number of plasma cloud is about 15. Over time, the Mach number of plasma flow decreases, resulting in the change of bow shock angle and shape. In addition, the width of the bow shock wave is about 50 渭 m, which is equivalent to the average collision free path between ions. The results show that the formation mechanism of the bow shock wave is mainly the collision effect between ions. A two-dimensional USIM fluid program is used to simulate the interaction between the plasma cloud and the barrier. The simulation results reproduce the experimental results well. Secondly, the interaction between the solar wind and the comet is simulated by using the plasma produced by the high power laser irradiation on the solid target. Through shadow and interference imaging diagnosis, the plasma tail with broken structure was successfully observed behind the obstacle. By means of particle program simulation, we find that the great difference in thermal velocity between ions and electrons in the plasma after impact creates an electric field behind the barrier, and the electric field attracts the ions to converge toward the middle. The intermediate plasma density increases to form a tail and a density jump structure appears at the front end of the tail. The results reveal another possible cause of comet tail breakage. Finally, the circular strong magnetic field around the wire is obtained by using a strong laser beam. The intensity of the magnetic field is measured by B-dot probe, and the spatial distribution of the magnetic field is calculated by simulation. The effect of magnetic field on bow shock wave is studied by supersonic plasma impinging on the wire by interaction of intense laser with Ch plane target. The influence of magnetic field on bow shock wave is observed in the experiment. Through the conversion of the calibration rate of the laboratory astrophysics, it is proved that the ionization of metal wire plasma produced by strong x-ray from the Ch target irradiated by laser can be used to simulate the solar wind plasma.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P14

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