实验室研究化学物质主动释放形成的电离层空洞边界层的非线性演化

发布时间：2018-06-08 21:03

本文选题：电离层空洞 + 边界层过程　；参考：《中国科学技术大学》2015年博士论文

【摘要】：电离层是地球大气的一个电离区域,其存在对大气电学和地球磁层的形成起着重要作用。电离层活动异常会对空间及地面技术系统造成严重危害,尤其是随着人类活动范围的进一步扩大,无线电通讯、卫星导航、航天器飞行、空间天气预报等活动都会受到电离层变化的影响。因此开展人工影响电离层空间天气的研究具有重要意义,而化学物质释放扰动电离层形成电离层空洞就是一种可行的人工影响空间天气的方法。电离层空洞可以影响无线电波的传播、高功率微波加热电离层的效率等一系列空间活动；同时在基础研究方面也提出了许多亟待解决的问题,例如电离层空洞边界层存在着从离子频率到低混杂频率的等离子体不稳定性,而这些不稳定性的产生与增长是电离层空洞的演化过程必须考虑的因素。因此,化学物质释放形成电离层空洞的研究是一个兼具国防安全和基础等离子体物理前沿的研究课题。世界各国科学家在过去几十年进行了大量化学物质主动释放制造电离层空洞空间实验和数值模拟研究。由于空间主动实验的主要手段依赖于相干散射雷达、非相干散射雷达、全天光谱仪以及一些地基、箭载和星载设备,这些对设备磁流体大尺度的物理问题研究很有优势。但是设备自身时间空间分辨率的限制,对电子离子混杂不稳定性这样的动理学尺度的不稳定性过程目前并没有很好的研究结果。我们在实验室等离子体中研究了化学物质主动释放形成电离层空洞边界层的非线性演化,首先验证了实验室环境下研究电离层空洞的可行性。由于空气辉光放电的组分和化学过程都接近于真实电离层环境,本论文采用空气辉光放电等离子体来模拟电离层环境。在背景等离子体形成之后,我们释放SF6、CC12F2和C02进入等离子体来形成模拟电离层空洞。实验采用微波干涉法和光谱法来研究模拟电离层空洞的演化,观察到了密度梯度随着等离子体气压和释放比例的演化,发现不同化学物质释放造成的密度梯度与空间主动实验的观测结果相一致。同时,我们还发现负离子中间产物(NI)物质比正离子中间产物(PI)物质降低电子密度效果明显；并且NI物质形成电离层空洞需要的时间较PI物质更短。这些结果与相应的空间主动实验观测结果一致。同时,我们还观察到了SF6释放造成777.4m的气辉增强和C02释放造成的630nm的气辉增强,这与全天光谱仪观测的结果一致。证明实验室等离子发生着和主动空间实验相同的过程,从而验证了我们研究方法的可行性。在此基础上我们发展了一种在实验室环境下研究电离层空洞产生与演化的方法,即通过无量纲参量定标的方法在实验室中产生ωpe/ωce、β值等一系列无量纲参量与真实空间环境相同或接近的等离子体；基于此我们可以在实验室实现和空间等离子体相同的物理过程。由于实验室环境下,可通过控制实验参数实现对电离层空洞边界层的物理问题进行详细研究。同时实验室等离子体诊断的时空分辨率相比空间观测都有较大优势,因此实验室环境通过定标方法可以精确研究电离层空洞边界层演化等微观物理问题。我们通过该方法在实验室研究了电离层空洞边界层的非线性演化过程,得到了边界层等离子体电子密度和等离子体电势的演化过程。我们观测到边界层上存在巨大的密度梯度Vn。和等离子体电势中f上升,发现在边界层电子密度梯度Vn。为等离子体电位涨落提供自由能。由于等离子体悬浮电位中f的变化会导致非均匀电场E(r)的产生,进一步在边界层激发剪切E×B流的产生。剪切流会驱动一系列从离子频率到混杂频率的等离子体不稳定性。通过对电子密度和等离子体电位的涨落做数字信号谱分析,我们发现悬浮电位涨落中存在一个低混杂频率范围内波结构。通过对该结构进行互功率谱分析和双谱分析,我们证实了该结构为剪切流驱动的电子离子混杂不稳定性(Electron-Ion Hybrid Instability)形成的的涡状相干结构。边界层电子离子混杂不稳定性的增长以及涡状相干结构的形成对电离层空洞的非线性演化起着重要作用。例如,边界层密度不规则体的形成就与电子离子混杂不稳定性相关。我们在实验室发现了该结构的存在对解释诸多空间主动实验的观测结果具有重要意义。我们还研究了电离层空洞边界层出现的电磁涨落。磁探针的信号显示,边界层上存在较强的电磁涨落。该涨落具有BT、BZ和Bθ分量,并且θ的分量远远大于其他分量。数字信号谱分析显示磁场涨落中存在一个低混杂频率的结构。经过对信号进一步进行互相关分析,我们发现这是右旋极化的哨声模式。并且通过静电电子离子混杂模式和电磁模式的频率对比,我们判断该哨声模式来源于静电电子离子混杂模式的非线性散射,这是首次给出从静电频率向电磁频率转化的实验证据。总之,我们在实验室环境下研究了化学主动释放形成的电离层空洞边界层的演化过程。通过采用无量纲参量定标的方法,我们研究了该区域的静电涨落和电磁涨落；发现了静电电子离子混杂模式以及其电磁波段哨声模式存在的证据,同时间接证明了边界层静电电子离子混杂模式可以经过非线性散射转化为电磁哨声模式。这些静电以及电磁涨落对边界层的演化过程动力学行为起着重要作用。由于实验室研究能够对许多空间观测不到的微观物理能进行详细研究,因此它能与目前电离层空洞的主要两种研究方法(空间主动实验和数值模拟)形成了一个很好互补效果,为国家即将开展的主动空间实验研究积累经验。
[Abstract]:The ionosphere is an ionizing region of the earth's atmosphere. Its existence plays an important role in the formation of atmospheric electricity and the formation of the earth's magnetosphere. The abnormal ionospheric activity will cause serious harm to space and ground technology systems, especially with the further expansion of human activities, radio communication, satellite navigation, spacecraft flight, space weather preconditioning. Newspapers and other activities are affected by the ionosphere change. Therefore, it is of great significance to carry out the research on the artificial influence of the ionosphere space weather, and the release of ionosphere by chemical substances to the ionosphere is a feasible method to affect the space weather artificially. The ionosphere cavity can affect the propagation of radio waves, high power microwave The efficiency of heating the ionosphere is a series of space activities, and there are many problems to be solved in basic research, such as the plasma instability in the ionospheric hole boundary layer from ion frequency to low hybrid frequency, and the generation and growth of these instability is an examination of the evolution process of the ionosphere cavity. Therefore, the study of the release of ionospheric cavities by chemical substances is a research topic with the frontiers of national defense security and basic plasma physics.
In the past few decades, scientists around the world have carried out a large number of chemical substances actively releasing the ionospheric cavity space experiments and numerical simulation studies. The main means of space active experiment depend on coherent scattering radar, incoherent scattering radar, all day spectrometer, and some ground, rocket and spaceborne equipment. The physical problem of large scale has a great advantage. However, the limitation of the time and space resolution of the equipment and the instability process of the kinetic study scale such as the electronic ion hybrid instability have not been well studied.
We have studied the nonlinear evolution of the active release of chemical substances into the ionospheric hole boundary layer in the laboratory plasma. First, the feasibility of the ionospheric cavity study in the laboratory environment was verified. The air glow discharge is used in this paper because the components and chemical processes of the air glow discharge are close to the real ionospheric environment. The plasma is used to simulate the ionosphere environment. After the formation of the background plasma, we release SF6, CC12F2 and C02 into the plasma to form an simulated ionospheric cavity. The experiment was conducted by microwave interference and spectroscopy to study the evolution of the simulated ionosphere cavity, and the evolution of the density ladder was observed with the evolution of the plasma pressure and release ratio. It is found that the density gradient caused by the release of different chemicals is in accordance with the observational results of the space active experiment. At the same time, we also found that the negative ion intermediate product (NI) material is more effective than the positive ion intermediate (PI) material to reduce the electron density; and the time required for the formation of the ionospheric cavity by the NI substance is shorter than that of the PI. At the same time, we also observed the enhancement of the gas glow of the 630nm resulting from the enhancement of 777.4m's air glow and the release of C02 by the release of SF6, which is in accordance with the results of the whole day spectrograph observation. It is proved that the laboratory plasma has the same process as active space testing, which proves our research side. The feasibility of the law.
On this basis, we have developed a method to study the generation and evolution of ionospheric cavity in laboratory environment, that is, we can produce Omega pe/ Omega CE, beta value and a series of non dimensional parameters that are the same or close to the real space environment in the laboratory by the method of dimensionless parametric calibration. The physical process is the same as space plasma. In the laboratory environment, the physical problems of the ionospheric hole boundary layer can be studied in detail by controlling the experimental parameters. At the same time, the space-time resolution of the laboratory plasma diagnosis is superior to that of the space observation. Therefore, the laboratory environment can be refined by the calibration method. It is necessary to study the microcosmic physics problems of ionospheric void boundary layer evolution.
We have studied the nonlinear evolution process of the ionospheric hole boundary layer by this method, and obtained the evolution process of the plasma electron density and plasma potential in the boundary layer. We observed that there is a huge density gradient Vn. and a f rise in the plasma potential on the boundary layer, and the electron density gradient Vn. in the boundary layer is found. The free energy is provided for the plasma potential fluctuations. Due to the change of F in the plasma suspension potential, the generation of E (R) in the non-uniform electric field will lead to the generation of the shear E x B flow at the boundary layer. The shear flow will drive a series of plasma instability from the ion frequency to the hybrid frequency. We found a low hybrid frequency range internal wave structure in the fluctuation of the suspended potential. Through the cross power spectrum analysis and the bispectrum analysis of the structure, we confirmed that the structure is a shear flow driven electron ion hybrid instability (Electron-Ion Hybrid Instability). The growth of the electron ion hybrid instability in the boundary layer and the formation of the vortex coherent structure play an important role in the nonlinear evolution of the ionospheric cavity. For example, the formation of the irregular body of the boundary layer density is related to the electronic ion hybrid instability. The observation results of space active experiments are of great significance.
We also studied the electromagnetic fluctuations in the ionospheric hole boundary layer. The magnetic probe signals show that there is a strong electromagnetic fluctuation on the boundary layer. The fluctuation has BT, BZ and B theta components, and the component of theta is far greater than that of the other components. Further cross-correlation analysis shows that this is the whistler mode of the right spin polarization. And by comparing the frequency of the electrostatic electron ion hybrid mode to the electromagnetic mode, we judge that the whistler model comes from the nonlinear scattering of the electrostatic electron ion hybrid mode. This is the first time to give the experiment of conversion from the electrostatic frequency to the electromagnetic frequency. Evidence.
In a word, we studied the evolution process of the ionospheric boundary layer formed by chemical active release in the laboratory environment. By using the method of dimensionless parametric calibration, we studied the electrostatic fluctuations and electromagnetic fluctuations in the region, and found the evidence for the existence of the electrostatic electron ion hybrid mode and the whistler mode of its electromagnetic wave band. It is also proved indirectly that the electrostatic ion hybrid mode in the boundary layer can be transformed into an electromagnetic whistle mode through nonlinear scattering. These electrostatic and electromagnetic fluctuations play an important role in the dynamic behavior of the evolution process of the boundary layer. Therefore, it can form a good complementary effect with the two main research methods (space active and numerical simulation) of the current ionospheric cavity, and it can accumulate experience for the country's forthcoming active space experiment.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P352

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