摘要
喷流的触发机制、准直传输和稳定性一直是天体物理学的研究热点.近年通过观测和实验室研究发现磁场在喷流准直传输和加速中起着关键作用.本文利用开源的辐射磁流体模拟程序FLASH对强激光驱动聚苯乙烯(CH)平面靶产生的靶前喷流进行了二维的数值模拟,系统地考察和比较了Biermann自生磁场以及不同方向、不同初始强度的外加磁场对喷流演化的动力学.模拟结果表明Biermann自生磁场不会影响喷流的界面动力学,而外加磁场对等离子体出流具有重定向作用,平行于靶前等离子体出流中心流向的外加磁场有助于喷流的产生和准直传输.其形成和演化过程是等离子体热压、磁压以及冲压三者相互竞争的结果.在受力方面,在喷流演化过程中等离子体热压梯度力和磁压力起决定性作用.研究结果为后续开展和喷流相关的实验研究提供借鉴,也有助于加深对天体喷流演化的理解.
Astrophysical jets are highly collimated supersonic plasma beams distributed across various astrophysical backgrounds.The triggering mechanism,collimation transmission,and stability of jets have always been a research hotspot of astrophysics.In recent years,observations and laboratory research have found that the magnetic field plays a crucial role in jet collimation,transmission,and acceleration.In this work,the twodimensional numerical simulation of the jet in front of the CH plane target driven by an intense laser is carried out by using the open-source MHD FLASH simulation program.We systematically investigate the dynamic behaviors of jet evolution caused by the Biermann self-generated magnetic field,the external magnetic field with different directions and initial strengths and compare them with each other.Simulation results show that the Biermann self-generated magnetic field does not affect the jet interface dynamics.The external magnetic field has a redirecting effect on the plasma outflow.The external magnetic field,which is parallel to the direction of the plasma outflow center in front of the target,is conducive to the generation and collimation of the jet.The evolution of the jet goes through three stages:antimagnetic ellipsoid cavity,conical nozzle,and collimated jet.Its formation process and evolution process result from competition among plasma thermal,magnetic,and ram pressure.In terms of force,plasma thermal pressure gradient and magnetic pressure forces play a decisive role in the jet evolution process.The presence of magnetic pressure significantly limits the radial expansion of the jet to achieve axial collimation transmission.The length-diameter ratio of the jet is positively correlated with the initial axial applied magnetic field intensity.In addition,we observe in the simulation that there are many node-like structures in the jet evolution zone,similar to the jet node in YSO.The results provide a reference for future experimental research related to jets and contribute to a more in-depth understanding of the evolution of celestial jets.
作者
孙伟
吕冲
雷柱
王钊
仲佳勇
Sun Wei;LüChong;Lei Zhu;Wang Zhao;Zhong Jia-Yong(Institute for Frontiers in Astronomy and Astrophysics,Beijing Normal University,Beijing 102206,China;Department of Nuclear Physics,China Institute of Atomic Energy,Beijing 102413,China;Institute of Applied Physics and Computational Mathematics,Beijing 100094,China;Department of Astronomy,Beijing Normal University,Beijing 100875,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2023年第9期297-306,共10页
Acta Physica Sinica
基金
国家自然科学基金(批准号:12205382,U2267204,12005305)
中国科学院战略性先导研究计划(批准号:XDA25030700)
中国原子能科学研究院核物理研究所所长基金资助的课题。
关键词
强激光
磁场
喷流
strong laser
magnetic field
jet