【作者】 马保科；

【导师】 郭立新；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2013， 博士

【摘要】 从随机媒质电波传播与散射理论出发，本文紧密围绕电离层本身的特性以及它对无线电波传播的各种影响展开。从目前这一领域的研究现状和存在的主要问题可以看出，由于电离层随机媒质本身的复杂性和时变性，使得对电离层随机媒质电波传播领域问题的研究至今仍然存在许多不确定和亟待解决的问题，而这些问题的存在严重影响了无线电系统的正常运营和工作效率的提高。故本文将研究工作的重点放在了电离层本身的一些特性以及它对无线电波传播影响的各种效应的研究上。研究内容主要包括：电离层电导率的时空分布特性、电离层电子密度不均匀体的漂移特性、电离层离子速度分布函数及其非相干散射特性、电离层闪烁特性以及电离层电波传播的时延及频移特性等与电离层电波传播息息相关的热点问题。本文主要深入开展了如下几个方面的工作：第一、从电离层电导率的理论研究出发，本文分析了电离层电导率以及极区场向电流的空间分布特征；利用国际参考电离层IRI模型，分析了地磁平静条件下，一个完整的太阳活动周内，极区Pedersen和Hall电导率在四个不同太阳活动周相内的变化；并对F2层上电导率的“冬季异常”展开了研究。另外，鉴于国际参考电离层模型并不能较好地反映电离层扰动或暴时高纬电离层电子密度的变化，故本文又从极区电离层沉降离子平均能量和能通量出发，分析了在不同的沉降离子能谱分布函数和地磁活动下，电离层电导率与沉降粒子能通量和平均能量的关系，暴时电离层电导率与F层电离耗空以及E层电子焦耳加热之间的关系，并就典型的电离层事件作出了分析。第二、在强、弱起伏下，本文对平静和暴时电离层电子密度不均匀体的漂移特征进行了分析：并就不同的电离层闪烁事件中不均匀体的漂移速度进行了反演研究。另外，基于空间接收机技术，利用“多站一星”法，并结合闪烁信号的互相关分析测量了电离层不均匀体的漂移速度，并将估算结果与时间功率谱法得到的结果进行了比较分析。第三、本文通过简化玻耳兹曼离子速度非麦克斯韦分布函数的积分解，得到了高纬电离层离子速度的环形分布函数，并进一步模拟和图解分析了离子速度分布函数呈环形分布的特征。另外，基于离子温度各向异性，且考虑比较强的电离层对流电场以及离子碰撞的影响，本文模拟并讨论了当离子速度分布函数呈环形时，不同方向上离子非相干散射谱的特点。第四、在对电离层电波闪烁理论研究的基础上，本文对中、高纬地区电离层电波闪烁的观测数据进行了统计分析。具体是：利用海南地区1991年7月到1993年7月近两年的电离层闪烁观测数据，对太阳活动下降年期间中纬、赤道地区GPS L波段的电离层闪烁进行了统计分析。同时，以太阳活动低年为时间节点，对意大利INGV（Istituto Nazionale di Geofisica e Vulcanologia）高纬电离层闪烁监测网以及我国南极中山站的电离层GPS L波段电离层闪烁进行了为期一年的统计分析，对比分析了GPS L波段电离层闪烁的中纬、赤道、高纬以及极区特征，分析了GPSL波段信号振幅、相位闪烁的时空分布随电离层电子浓度总量TEC及其变化率ROT、电子密度起伏方差、太阳黑子数、季节以及行星际磁场IMF的变化。第五、在分层媒质电波传播及相位屏理论的基础上，本文将电离层假设为一各向同性、均匀的平面分层媒质，推导了电波经电离层反射回波信号的多普勒频移公式。同时，基于瑞利衰落假设，从理论上得到了电波多径时延与多普勒频移之间的概率密度关系，并针对具体的电路进行了分析。最后，在多相位屏(MPS)理论的基础上，得到了电波向上和向下传播电离层（即双程传播）时，电波电离层回波场的具体表达式。理论研究表明：相比于几何光学近似(GO)，多相位屏理论既考虑了电波场的振幅变化，又考虑了电波场的相位起伏，具有明显的优势。更多还原

【Abstract】 On the basis of theoretical study of electromagnetic wave propagation and scatteringin random media, the background ionosphere and the electron density irregularities thatlocate in the ionosphere which effect on the radio wave propagation have been studiedin this dissertation. From the status of current research and the open questions in thisarea we can see that there are still many uncertain factors and the outstanding issues inthis area due to the complexity of the ionospheric random medium itself, and which hasseriously influence on the normal operation of the radio wave system and its workefficiency improving. Therefore, the thesis will focus primarily on researching somecharacteristics of the ionosphere itself and its various effects on radio wave propagation.The research contents include: the temporal and spatial distribution characteristics of theionospheric conductivity, the drift characteristics of the ionospheric electron densityirregularities, the ion velocity distribution function and its characteristics of theincoherent scattering, the ionospheric scintillation, as well as the characteristics of thetime delay and the frequency shift for the radio wave propagation, which are all thecurrent hot issues in this field. The main topics in the dissertation are as follows:Firstly, the changes of the Pedersen and Hall conductivity for four different solaractivity phase in the high latitude ionosphere is discussed, and the winter abnormaldistributon of the conductivity in the F2layer is also analyzed. In addition, therelationship between the ionospheric conductivity and the ionizing consumption whichtakes place in the F layer and the electronic Joule heating which appears in the E-layerat the storm time are all studied.Secondly, the drift velocity of the ionospheric irregularities for the calm and the stormtime is inversed. Meanwhile, based on the space receiver technology and the“multi-station one satellite” method, the drift velocity of the ionospheric irregularitieshas been estimated successfully, and the estimated results were compared with theresults that obtained from the time power spectra method finally.Thirdly, with the relative larger electric field strength, the torus velocity distributionfunction for ions is obtained at the high latitude ionosphere, and the characteristic of thetorus velocity distribution function is also simulated and analyzed. Meanwhile, takinginto account the ion temperature anisotropy, the collision with other ions and itsvariation with the ionospheric electric field, the incoherent scattering power spectrum ofion in different direction is simulated and discussed.Fourthly, the ionospheric scintillation data of GPS L-band in mid-latitude of HainanChina for the period of July1991to July1993during the lower solar activity isstatistically analyzed. Meanwhile, takes the year of the lower solar activity as a timenode, the high-latitude ionospheric scintillation data which comes from the INGV (Istituto Nazionale di Geofisica e vulcanologia) scintillation monitoring networks ofItalian as well as from the Zhongshan Station of China for a period of one year are alsostatistically analyzed and discussed. At the same time, the scintillation characteristics atthe mid-latitude ionosphere are compared with it at the high latitude region at the GPS Lfrequency band is given.Finally, assuming that the ionosphere is a homogeneous, isotropic, stratified media, theDoppler shift formula of the echo signals of the radio wave is derived. And with theassumption of the Rayleigh fading, the probability density distribution of the multi-pathtime delay and the Doppler shift of the ionospheric radio signal are also derived,moreover, the probability density distribution of the time delay, the average power ofthe received signal, and the received signal variance changes with the time delay spreadare discussed in detail. Moreover, based on the theory of the multiple phase screen(MPS), the echo field expression that the radio wave propagates through the ionosphereup and down (i.e. double path propagation) are obtained. The research shows thatcomparing with the geometrical optical approximation (GO), the method of the multiplephase screen no only takes into account the changes of the amplitude of the radio wave,but also considering the variation of the phase, and its advantages is obvious.更多还原