Study On The Interaction Between Interstellar Medium And Planets With High-power Lasers In Laboratory

Laboratory astrophysics is a frontier subject in the field of high energy density physics and astrophysics.With the rapid development of laser technology,laser has become an important experimental instrument in laboratory astrophysics.With highpower lasers,the extreme physical conditions of the celestial bodies can be created in laboratory experiments,so that the process and mechanism of astrophysics can be studied in a comprehensive,deep and controllable way.This thesis mainly focuses on the processes,commonly occurring in the universe,of interstellar medium interactions with stars or planets.The related physical mechanisms and phenomena are studied theoretically and experimentally.Firstly,this thesis carries out a bow shock experiment by means of high-speed laser-driven plasma cloud,produced by the high power laser irradiation on a CH plane target,interacting with a cylindrical obstacle.The bow shock with a high Mach number is formed.The formation and evolution of the bow shock wave are successfully observed by shadow and interference imaging diagnosis.At 1 ns delay time,the Mach number of the plasma cloud is up to 15.As time goes by,the Mach number is reduced,causing the change of the opening angle and the shape of bow shock structure.In addition,the bow shock width is measured to be ~50 ?m,equivalent to the ion-ion collision mean free path.It indicates that collision dominates the shock probably.We also simulate the process of the interaction between the plasma cloud and the obstacle by using the two-dimensional USim fluid program.The simulated shocks can well reproduce the observed.Secondly,the process of the interaction between the solar wind and the comet is simulated by using the plasma produced by high power lasers.A disconnected plasma tail is observed by shadowgraphy and interferometry.With particle-in-cell simulations,it is found that the difference in thermal velocity between ions and electrons induces an electrostatic field behind the obstacle.This field can lead to the convergence of ions to the central region,resulting in a disconnected plasma tail.This electrostatic-fieldinduced model may be a possible explanation for the disconnection events of cometary tails.At last,we use the model of high power lasers irradiating a metal wire to produce a strong magnetic field.The magnetic field intensity is measured by B-dot detectors.The magnetic field distribution is calculated with a three-dimension code.A bow shock is formed in the interaction of a high-speed laser-driven plasma with the metal wire.The effects of the strong magnetic field on the bow shock are observed by shadowgraphy and interferometry.It is showed that the Mach number of the plasma flow is decreased by the magnetic field,leading to an increase of opening angle of the bow shock and decrease of the density ratio between downstream and upstream.According to the similarity criteria,the experimental parameters of plasma are scaled to those in the space.The transformed results show that the magnetized plasma in the experiment is suitable for simulating solar wind in astrophysics.