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基于地球-电离层空腔共振的地震电磁监测方法研究 总被引：1，自引：0，他引：1
多年来的观测研究表明,地震活动可能引发地球．电离层空腔共振异常。本文介绍了地球-电离层空腔共振的产生机理,主要的特征参数以及常用的观测方法等。总结了目前国际上对共振异常现象与地震活动关系的主要分析方法和研究结果。对地震活动引发地球-电离层空腔共振异常的下一步研究工作进行了探讨。 相似文献
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2.1地震孕育和发生过程中的电异常现象
2.1.1地电场及震前地电场异常.地球表面存在着天然的变化电场和稳定电场,天然变化电场的大部分是由地球外部各种电流系在地球内部感应产生的,分布于整个地表的广大地区,一般具有较小的梯度;另外还有一小部分是由于地球内部的某些地球物理、化学变化产生的,出现在某些特定的时间和区域,一般也具有较小的梯度变化,但有时可能引起较大的电位梯度变化. 相似文献
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利用高频泵波能对低电离层进行有效的人工扰动.采用ELF/VLF调幅高频电波对电离层进行加热,电子温度会随着调制频率振荡,并引起电导率周期性变化,从而使加热区内电离层电流周期性变化,形成等效的ELF/VLF电离层虚拟天线,辐射调制频率范围内的无线电波.早期的电离层人工调制研究主要集中在高纬和极区,本文讨论低纬地区电离层人工调制的可能性.本文的理论研究和数值模拟结果表明,低纬地区低电离层电导率在周期性加热的条件下能有效地被调制,使加热区域形成ELF/VLF波的电流辐射源,并分析了不同加热参数和入射条件对调制效果的影响. 相似文献
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利用离子和电子动量方程、连续性方程以及电流连续性方程建立了适合描述中低纬spread-F发展的物理模型,并对模型进行了数值求解,讨论了利用H2O释放来激发电离层Rayleigh-Taylor不稳定性的可能性. 结果表明,电离层处于不稳定状态时,H2O在电离层底部释放后,造成电子的大量消耗,增强了峰值高度以下电子的密度梯度,有利于spread-F的发展,在spread-F发展的过程中,释放中心附近会形成电子密度的消耗区,两侧出现密度的增强区;而电离层比较稳定时,初始扰动会逐渐稳定下来,但化学物质释放仍能造成电子较长时间、较大范围的扰动. 相似文献
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太阳带电粒子流通过磁边界层的中性点或阻塞点,由于极化电場的漂移运动或雷萊-泰勒（Rayleish-Taylor）不稳定运动,穿透磁层而进入地磁場被輻射带所捕获。这些被捕获的电子将向东漂移而形成西向电流。在它們围繞地球一周形成封閉的电流环以前,由于地球的自轉以及这个电流弧对地球各地的相对位置的不同,电流分布以及它在地面磁赤道附近所产生的磁場分布都将是不均匀的,对經度来耕是不对称的。本文假定电子繞地球的漂移周期为两天,計算了当磁暴开始时位于地方时00,06,12及18小时的台站記录的磁場随“暴时”Tst变化的曲线。理論結果与用佘山及洪伽幼地磁台站得到的統計結果是一致的。 相似文献
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为了在深部第二成矿带找矿,需要进一步提高电磁法可控源的强度,因此,一种新的大功率固定发射源的电磁法正在孕育之中.该方法采用长偶极源或者环状电流源,为了提高发射源的强度,偶极长度L或者环状源半径R需要非常大.然而,电磁场信号的强度不仅仅依赖于发射源,当L或者R为数十公里时,接收点的位置远离发射源,电离层对电磁场的影响不可以忽略.电离层的影响既可能是增强信号,也可能是削弱信号,这依赖于不同类型源产生的电磁波.本文利用三维积分方程法对包含电离层、空气层、固体地球层(简称地-电离层模型)的线状和环状大功率电流源电磁波响应进行了三维数值模拟,对两种源的电磁波的响应特征进行了对比研究.研究表明虽然磁性源的发射效率高于电性源,但是由于发射源在波导区产生的直达波经电离层的反射波要产生相长相消干涉,波导区的场特征既和发射源的特征有关,也和电离层有关.对比研究发现对于x方向的水平长偶极源电离层对电磁场 Ex 和 Hy 的影响是使场的幅值增强,即波导场的 Ex 和 Hy 的衰减是减缓的.而对于水平环状电流源,电离层对水平方向的电磁场的影响是使场的幅值减弱,即波导场的 Ex 和 Hy 的衰减是增大的.为此,认为采用大功率固定源在波导场工作时应该采用线状电流源. 相似文献
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Friedemann Freund 《Acta Geophysica》2013,61(4):775-807
Most destructive earthquakes nucleate at between 5–7 km and about 35–40 km depth. Before earthquakes, rocks are subjected to increasing stress. Not every stress increase leads to rupture. To understand pre-earthquake phenomena we note that igneous and high-grade metamorphic rocks contain defects which, upon stressing, release defect electrons in the oxygen anion sublattice, known as positive holes. These charge carriers are highly mobile, able to flow out of stressed rocks into surrounding unstressed rocks. They form electric currents, which emit electromagnetic radiation, sometimes in pulses, sometimes sustained. The arrival of positive holes at the ground-air interface can lead to air ionization, often exclusively positive. Ionized air rising upward can lead to cloud condensation. The upward flow of positive ions can lead to instabilities in the mesosphere, to mesospheric lightning, to changes in the Total Electron Content (TEC) at the lower edge of the ionosphere, and electric field turbulences. Advances in deciphering the earthquake process can only be achieved in a broadly multidisciplinary spirit. 相似文献
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Measuring the low-energy ions in the Earth's magnetotail lobes is difficult, because a spacecraft becomes positively charged in a sunlit and tenuous plasma environment. Recent studies have introduced a new method, making use of the positive electric potential on the Cluster spacecraft, to measure the low-energy ions(less than a few tens of electronvolts) in the polar caps/magnetotail lobes in the years 2001–2010. With the measured velocities, we are able to study the trajectories of these low-energy ions. Particle tracing has been used in previous studies, confirming that ions of ionospheric origin are the dominant contributor to the ion population in the Earth's magnetotail lobes. In this work, we continue to study the source of low-energy ions measured in the lobes. We found that not all of the low-energy ions in the lobes come directly from the ionosphere. Particle tracing infers that some of the low-energy ions start to move tailward from the cusp/near-cusp region with a zero parallel velocity. In the following, we refer to these low-energy ions as stagnant low-energy ions. On the other hand, the in situ measurements by Cluster show a population of low-energy ions in the cusp/near-cusp region with pitch angles near 90°(i.e., no significant parallel velocity).The locations of stagnant low-energy ions are determined by particle tracing and in situ measurements. Similar ion energies and spatial distributions determined by these two methods confirm the presence of the stagnant low-energy ion population. 相似文献
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Physical mechanisms of man-made influences on the magnetosphere 总被引：3，自引：0，他引：3
Since the discovery of the Luxembourg effect in the 1930s, it is clear that man-made activities can perturb the ionosphere and the magnetosphere. The anthropogenic effects are mainly due to different kinds of waves coming from the Earth's surface. Acoustic-gravity waves are generated by large explosions, spacecraft launches, or flight of supersonic planes. Electromagnetic waves are active in different frequency ranges. Power line harmonic radiation which is radiated in the ELF range by electrical power systems can be observed over industrial areas. At VLF and HF, the ground-based transmitters used for communications or radio-navigation heat the ionosphere and change the natural parameters. A large variety of phenomena is observed: wave-particle interaction, precipitation of radiation belt electrons, parametric coupling of EM whistler waves, triggered emissions, frequency shift, and whistler spectrum broadening. This paper will review the different physical mechanisms which are relevant to such perturbations. The possibility of direct chemical pollution in the ionosphere due to gas releases is also discussed. 相似文献
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E. V. Pomozov 《Geomagnetism and Aeronomy》2014,54(1):127-134
In the used model, the quasistationary electric field in the atmosphere of the Earth is obtained by solving the conductivity equation. The penetration characteristics of the electric field from the Earth’s surface into the ionosphere depend on both atmospheric and ionosphere conductivity. The ionosphere is taken into account by setting a special condition on the upper boundary of the atmosphere. The influence of the atmospheric surface layer with a reduced conductivity on the penetration of the electric field from the surface of the Earth into the ionosphere is analyzed. 相似文献
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Yingying Fan Xuebin Du Zhanghui An Jun Liu Dacheng Tan Junying Chen 《Acta Geophysica》2015,63(3):679-697
The changes of the ionospheric electric field before and after four huge earthquakes, which include the Ms 8.7 earthquake of 2004 and the Ms 8.5 earthquake of 2005 in Sumatra of Indonesia, the Ms 8.0 Wenchuan earthquake of 2008 in China, the Ms 8.8 earthquake of 2010 in Chile, and their strong aftershocks are studied in this paper. The significant results revealed that the power spectral density of low-frequency electric field below 20 Hz in the ionosphere, a kind of electromagnetic radiation phenomena, increased abnormally before and after the earthquakes and partially corresponded to the increased power spectral density of the low-frequency geoelectric field in time. This research preliminarily indicates that the low-frequency electromagnetic radiation during the imminent stages before such earthquakes could be detected by the observation of the ionospheric electric field. However, the spatial, temporal, and intensive complexities of the electric field anomalies in the ionosphere before earthquakes have come in sight also. 相似文献
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Friedemann T. Freund Ipek G. Kulahci Gary Cyr Julia Ling Matthew Winnick Jeremy Tregloan-Reed Minoru M. Freund 《Journal of Atmospheric and Solar》2009,71(17-18):1824-1834
Pre-earthquake signals have been widely reported, including perturbations in the ionosphere. These precursory signals, though highly diverse, may be caused by just one underlying physical process: activation of highly mobile electronic charge carriers in rocks that are subjected to ever increasing levels of stress. The charge carriers are defect electrons associated with O? in a matrix of O2?. Known as positive holes or pholes h, they flow out of the stressed rock into the unstressed rock volume, traveling meters in the laboratory, probably kilometers in the field. At the rock–air interface they cause: (i) positive surface potential, (ii) field-ionization of air molecules, (iii) corona discharges. The rate of formation of airborne ions can exceed 109 cm?2 s?1. Massive air ionization prior to major earthquakes increases the electrical conductivity in the air column and may cause ionospheric perturbations, earthquake lights, and unusual animal behavior as well as infrared emission. 相似文献
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本文利用DEMETER卫星VLF频段电场和磁场频谱数据对DEMETER卫星运行期间2005年至2009年澳大利亚甚低频(Very Low Frequency)通信台NWC发射的通信信号造成的电离层电磁响应的日变化、季节变化及年变化特征进行了统计分析,统计结果表明电磁响应日变化显著,夜间电场强度明显增强可达40dB,磁场变化略小也可为15dB左右,而季节变化不显著,年变化主要受太阳活动的影响,太阳活动越强,电磁响应越小.为解释数据分析结果,对地-电离层电磁波传播过程采用传递矩阵方法进行了模拟计算,模拟结果与数据分析的结果一致.我们认为这种随时间变化的特点可能由250km以下电离层电子密度分布特征导致,因此研究250km以下的电离层电子密度变化可能对寻找地震电离层电磁异常有重要意义. 相似文献
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This paper summarizes the years of studies devoted to the self-similarity of anomalies originating in the ionosphere above the regions of the preparation of strong earthquakes. Using statistical processing of data on electron density variations obtained by methods of vertical sounding and measurements of the total electronic content, we have formed a pattern of similar variations observed at midlatitudes before strong earthquakes; we call it a precursor mask for earthquakes. It was found that the positive anomaly in the ionosphere formed at nighttime after sunset and ended at sunrise. In the case of strong earthquakes, the anomaly can last 12 h and emerge within a few days at the same local time. We propose a physical mechanism of anomaly formation in the ionosphere bound with the diurnal dynamics of the atmospheric boundary layer, which regulates the height distribution of cluster ions. 相似文献
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Acoustic waves have a remarkable ability to transfer energy from the ground up to the uppermost layers of the atmosphere. On the ground, there are many permanent sources of infrasound, and also pulsed and/or sporadic sources (e.g., sea waves, infrasonic and sonic noise of cities, lightning, earthquakes, explosions, etc.). The infrasonic waves carry away the major part of their energy upwards through the atmosphere. What are the consequences of the upward energy transfer? What heights of the atmosphere are supplied by energy from various sources of an infrasonic wave? In most cases, the answers to these questions are not well known at present. The only opportunity to monitor the propagation of an infrasonic wave to high altitudes is to watch for its influence on the ionospheric plasma. Unfortunately, most of standard equipment for ionospheric sounding, as a rule, cannot detect plasma fluctuations in the infrasonic range. Besides, the form of an infrasonic wave strongly varies during propagation due to nonlinear effects. However, the development of the Doppler method of radiosounding of the ionosphere has enabled progress to be made. Simultaneously, the ionospheric method for sensing aboveground and underground explosions has been developed. Its main advantage is the remote observation of an explosion in the near field zone by means of short radio waves, i.e., the radio sounding of the ionosphere directly above the explosion. The theory of propagation of an acoustic pulse produced by an explosion on the ground up to ionospheric heights has been developed better than the theory for other sources, and has been quantitatively confirmed by experiments. A review of some advances in the area of infrasound investigations at ionospheric heights is given and some current problems are presented. 相似文献