【作者】 薛昆；

【导师】 郭立新； 吴健；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2009， 博士

【摘要】 本文以电离层等离子体的非麦克斯韦分布为出发点,围绕着非麦克斯韦离子分布函数的求解、非麦克斯韦非相干散射谱的计算以及高纬极区离子声波谱线增强的理论解释与实验分析开展了相关研究。由相关领域的研究现状和存在问题的分析可知,目前对于非麦克斯韦离子分布函数和非相干散射谱的求解还处于尝试阶段,同时离子声波谱线增强的理论解释也存在着很大的争论。所以本文将工作重点放在非麦克斯韦离子分布函数的求解,非麦克斯韦分布的电离层等离子体非相干散射谱的模拟以及离子声波谱线增强的理论解释和实验研究上。由于非相干散射雷达和电离层加热的发展,这些问题已经成为利用非相干散射雷达研究电离层的热点问题之一,亟待解决。作为研究工作的基础,本文首先介绍了电离层等离子体的基本理论。在此基础上,主要开展了如下工作:第一,基于电离层等离子体的非相干散射理论,在不考虑磁场的情况下,分别采用碰撞和非碰撞等离子体非相干散射谱密度的理论公式,对麦克斯韦分布下的分布函数以及非相干散射谱进行了模拟和讨论。第二,从玻耳兹曼方程出发,分别采用驰豫碰撞模型和麦克斯韦分子碰撞模型来描述玻耳兹曼碰撞积分项,基于麦克斯韦分布展开的5矩、13矩、20矩近似和双麦克斯韦分布展开的6矩、16矩近似来表示离子分布函数。结合两种碰撞模型下的输运方程,分别求解得到了驰豫碰撞模型和麦克斯韦分子碰撞模型下的各阶速度矩分量,将其代入分布函数的多项式中,获得了两种碰撞模型下离子分布函数的5矩、13矩、20矩、6矩以及16矩近似。对输运方程的解以及离子分布函数进行了数值模拟,同时对两种碰撞模型下输运方程的解以及分布函数进行了对比。第三,利用已经得到的驰豫碰撞模型和麦克斯韦分子碰撞模型下离子分布函数的多项式解,采用Sheffield的非相干散射理论对非相干散射谱进行了模拟。同时对驰豫碰撞模型和麦克斯韦分子碰撞模型下得到的非相干散射谱进行了对比分析。第四,考虑到非相干散射雷达在高纬极区电离层经常观测到的离子声波谱线增强的现象,分别采用现有的三种理论对离子声波谱线增强的现象进行了解释。通过在分布函数中引入场向热流项,对场向电流不稳定性,以及离子-离子双流不稳定理论进行了修正,使其更符合实际情况,从而更好地解释了离子声波谱线增强的现象。第五,联合EISCAT(European Incoherent Scatter)雷达观测数据和其他观测手段,例如光学手段(极光扫描光度计,全天空极光摄像机等),选取发生离子声波谱线增强的两次现象进行了讨论分析,找出可能引起发生离子声波谱线增强的原因。结合场向电流不稳定性和修正场向电流不稳定性对数据进行了分析,反演得到了相应的电离层等离子体参数。更多还原

【Abstract】 Based on the theoretical study of Non-Maxwellian ionosphere plasma, the Non-Maxwellian ion distribution function, the Non-Maxwellian incoherent scatter spectra and the interpretations from the theories and experiments on the origin of Naturally Enhanced Ion Acoustic Lines (NEIAL) in the high latitude auroral ionosphere are investigated in this dissertation. A thorough relevant research reveals that the study on the Non-Maxwellian ion distribution and the Non-Maxwellian incoherent scatter spectra is just a preliminary work, and the interpretation on the origin of NEIAL also remains controversial. Consequently, this dissertation focuses on the work of the Non-Maxwellian ion distribution, the Non-Maxwellian incoherent scatter spectra and the interpretation on the origin of NEIAL. With the development of the incoherent scatter radar and the ionospheric heating, this field has become one of the hot topics in ionospheric study using the incoherent scatter radar, and is in urgent need for further study. As a basis of this dissertation, a brief review is firstly presented on the characteristics of the ionosphere plasma. The main works are as follows.Firstly, based on the incoherent scatter theories of ionosphere plasma, using the formulas of the incoherent scatter spectra of the collision and non-collision plasma without considering the magnetic field, the Maxwellian ion distribution function and the incoherent scatter spectra are calculated and discussed.Secondly, according to the Boltzmann’s equations, the Boltzmann collision integral is represented with a simple relaxation collision model and the Maxwell molecule collision model, respectively. The ion velocity distribution function is described by 5-moment approximation, 13-moment approximation and 20-moment approximation based on Maxwellian distribution or by 6-moment approximation, 16-moment approxi- mation based on bi-Maxwellian distribution, respectively. The ion temperature, the ion drift velocity, the ion temperature, the stress tensor and the heat flow vector are obtained from the transport equations of the relaxation collision model and the Maxwell molecule collision model, respectively. The expressions of the ion velocity distributions of 5-moment approximation, 13-moment approximation, 20-moment approximation, 6-moment approximation and 16-moment approximation are derived. The comparison of the solutions of the transport equations and the ion velocity distribution between the relaxation collision model and the Maxwell molecule collision model are discussed. Thirdly, using the ion velocity distribution of the relaxation collision model and the Maxwell molecule collision model, the incoherent scatter spectra are calculated with the Sheffield’s incoherent scatter theories. The comparisons of the incoherent scatter spectra obtained by above two collision models are discussed.Fourthly, considering the phenomenon of NEIAL, which have been frequently observed by incoherent scatter radar in the high latitude auroral ionosphere, three different theories available are discussed to interpret the origin of NEIAL in the auroral ionosphere. By introducing the field-aligned heat flow, the current driven ion acoustic instability and the ion-ion two stream instability are modified, which can interpret NEIAL better.Finally, combining the EISCAT radar data and the others related method of the observation, such as optical detection (Meridian scanning photometer, All Sky TV Camera), the two NEIAL events are selected and discussed, and reason for the NEIAL occurring is obtained. According to theories of the field-aligned current instability and the modified field-aligned current instability, the reasonable ionosphere plasma parameters are inversed and obtained from the incoherent scatter radar data.更多还原