钡和铯释放的电离层扰动效应对比  

Comparison between ionospheric disturbances caused by barium and cesium

作　　者：朱肖丽 胡耀垓[1] 赵正予[1] 张援农[1] Zhu Xiao-Li;Hu Yao-Gai;Zhao Zheng-Yu;Zhang Yuan-Nong(Ionosphere Laboratory,School of Electronics and Information,Wuhan University,Wuhan 430079,China)

机构地区：[1]武汉大学电子信息学院电离层实验室

出　　处：《物理学报》2020年第2期312-320,共9页Acta Physica Sinica

摘　　要：碱金属或碱土金属在电离层释放后,迅速在太阳辐射作用下发生光电离,产生正离子和电子,形成人工等离子体云团.本文基于三维双成分流体模型,考虑释放区域水平风场的影响,探讨了钡和铯在电离层释放后的时空演化规律,并对钡和铯的电离层扰动效应进行了对比.模拟结果表明,不考虑中性风场时,生成的等离子体云团逐渐沿磁场被拉伸成椭球形结构,同时,膨胀的等离子体云会推开背景氧离子,在释放中心形成氧离子密度空洞,并在两侧产生两个对称的密度尖峰;水平风场的存在会使得生成的离子云逆风侧的密度梯度变陡,释放物质对背景氧离子的扰动也更大;对比钡与铯的释放结果发现,由于铯的扩散系数较小,钡云的膨胀更为迅速,Ba+云团的覆盖区域更广;而由于光电离率较大,释放相同质量下铯的离子产率更高;此外,Cs+的扫雪机效应比Ba+扫雪机更强,氧离子密度空穴和凸起处的扰动也更大.After being released in the ionosphere,alkali-metal atoms will be rapidly photoionized by solar UV,producing positive ions and electrons,and forming artificial plasma cloud.Based on a three-dimensional twospecies fluid model,considering both the loss of barium atoms due to photoionization and oxidation and the influence of horizontal wind field in the release region,the spatial-temporal evolution of the artificial plasma cloud is discussed.By taking into account the electromagnetic field force,pressure gradient,particle collisions and ion inertia,the ionospheric disturbance effects caused by barium and cesium are compared with each other.The simulation results show that the alkali metal rapidly expands after being released in the ionosphere,and the generated plasma cloud gradually forms an ellipsoidal structure from the inside to the outside under the constraint of magnetic field with considering no wind.Meanwhile,the expanded plasma cloud pushes away the background oxygen ions,forming an oxygen ion density hole in the release center and two symmetrical density bumps on both sides.In the absence of neutral wind,the plasma cloud is dominated by the movement along magnetic field,while considering the background neutral wind,the plasma cloud and background disturbance area will move along the direction of wind,so that the density gradient of plasma cloud becomes steepening on the upwind side.Although the movement of ion cloud across the magnetic field is constrained,the neutrals can pass through the magnetic field freely,so the ion cloud and neutral cloud will separate from each other slowly.Also,the presence of horizontal wind field will make a greater disturbance to the background oxygen ion.By comparing the simulation results of barium and cesium we can see that,qualitatively,the expansion characteristics of Cs+and Ba+as well as their effects on the background O+are similar.Due to the small diffusion coefficient of cesium,the barium cloud expands more rapidly and the coverage area of Ba+cloud is wider.Because of

关 键 词：人工等离子体云团 中性扩散模型 三维双成分模型 扫雪机效应 

分 类 号：P352[天文地球—空间物理学]