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Summary The numerical method of simulating ionospheric filtration of ULF signals in the range of Pc1 frequencies has been applied to French geomagnetically conjugate observations of ULF signals made by the GEOS-1 satellite and at the observatory of Husafell (Iceland) [2]. The experimentally obtained variable values of the transmissivity of the Pc1 signal through the ionosphere [5] in the course of the micropulsation distrubance of 13.7. 1977 have been compared with the results of the numerical simulation taking into consideration the fundamental physical parameters of the high-latitude external ionosphere. This approximate form of solving the inverse problem of ionospheric modelling yielded quantitative estimates of the rapid variations of the concentration of charged particles in connection with the expected changes of their temperature. It is assumed that nonstationary states of the ionospheric plasma are caused by the very ion-cyclotron waves penetrating the ionosphere at high latitudes ( 70°) along the plasmapause. 相似文献
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Numerical simulation of the variations in the total electron content of the ionosphere observed before the Haiti earthquake of January 12, 2010 总被引：1，自引：0，他引：1
We present the results of a study of the abnormal variations in the total electron content (TEC) of the ionosphere observed before the earthquake of January 12, 2010, in Haiti. Global and regional maps of TEC relative (%) deviations from the quite background state are built for January 9–12, 2010. Using the UAM (Upper Atmosphere Model) global numerical model of the upper atmosphere of the Earth, the variations in the electric potential in the ionosphere and TEC are calculated using external seismic current above faults between the Earth and the ionosphere as a lower boundary condition. The numerical simulation results are compared with observations. It is shown that the simulated variations in the TEC at a specified current density of about 1 × 10?8 A/m2 on an area of 200 km (latitude) × 4000 km (longitude) above the focus represent all main features of the observations: prevalence of increased TEC values (positive disturbances), neighboring negative disturbances of lower magnitudes, localization, magnetic conjugacy of high-intensity effects in the Southern Hemisphere, and disappearance of disturbances around midday. Methodological recommendations are given to reveal variations in the TEC related to the preparation of seismic events. 相似文献
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The results of numerical simulation of the nonlinear evolution of an acoustic pulse propagating above an earthquake epicenter with preset energy parameters are presented. The interaction with charged plasma particles in the lower ionosphere is taken into account. The interaction between neutral and charged components is described by the diffusion mechanism of the disturbance of the density of charged ionospheric plasma components. The simulation was carried out for three values of earthquake magnitude M = 5; 6; and 7. It is ascertained that the numerical simulation results agree with analytical estimates made during the study of main regularities of seismic events that induce weak nonlinear effects in the atmosphere. 相似文献
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This work is devoted to a numerical simulation of the equatorial ionosphere, performed using the GSM TIP model completed with
a new block for calculating the electric field. It has been indicated that the usage of the wind system calculated according
to the MSIS-90 model makes it possible to reproduce the electromagnetic drift velocities at the equator, the effect of the
F2-layer stratification, and the appearance of the F3 layer in the equatorial ionosphere. The calculations performed using the modified GSM TIP model made it possible to detect
a maximum in the electron density vertical profile at an altitude of ∼1000 km, formed by H+ ions, which we called the G layer. If this layer actually exists, it can be observed during sounding the low-latitude ionosphere from satellites during
dark time of day. 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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M. Yu. Andreev D. V. Blagoveshchensky V. M. Vystavnoi V. S. Mingalev G. I. Mingaleva 《Geomagnetism and Aeronomy》2007,47(4):502-509
The experimental ionograms of the oblique-incidence sounding of the ionosphere, obtained on the St. Petersburg-Spitsbergen high-latitude HF radio path during the magnetically quiet period December 14–15, 2001, are compared with the model calculations of radiowave trajectories. For this purpose, the corresponding oblique-incidence ionograms are numerically synthesized using the technique based on the shooting method and the computer program for constructing HF radiowave trajectories. The three-dimensional electron density distribution, calculated using the mathematical model of the high-latitude ionosphere previously developed at the Polar Geophysical Institute (PGI), is used to model radio propagation. The numerical calculations make it possible mainly to explain the specific features of the experimental data on the oblique-incidence sounding of the ionosphere. 相似文献
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《Journal of Atmospheric and Solar》2000,62(16):1515-1525
We report on the first comprehensive numerical simulation of a space weather event, starting with the generation of a CME and subsequently following this transient solar wind disturbance as it evolves into a magnetic cloud and travels through interplanetary space towards Earth where its interaction with the terrestrial magnetosphere–ionosphere system is also predicted as part of the simulation. 相似文献
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参量衰减不稳定性(Parametric Decay Instability,PDI)在大功率高频(High frequency,HF)电波与电离层等离子体相互作用的过程中扮演着十分重要的角色,本文采用广义Zakharov方法对常规的等离子体流体力学方程组进行相应处理后,并在近似实际的电离层背景和电波传播模型下,构建了高频电波加热电离层激发PDI的数值计算模型.模拟结果发现:在毫秒量级的时间尺度上,大功率高频电波在寻常波(Ordinary wave,O波)反射点高度附近激发出了朗缪尔波(Langmuir wave)和离子声波(Ion-Acoustic wave)两种等离子体静电波模,模拟中产生的朗缪尔波和离子声波相应波数为5~11rad·m~(-1),结果与利用色散关系求出的理论值4~7 rad·m~(-1)近似一致,密度扰动幅值从10~6m~(-3)量级指数级增长到了10~(10)m~(-3)量级,直至能显著影响与"低频"密度背景相关的等离子体频率后,出现了等离子体"空穴"结构以及朗缪尔波被"俘获"现象,在扰动空间内的小尺度静电场幅值最高能达到100 V·m~(-1)量级,最终造成一种强烈的局地化"空穴"湍流现象.本文的研究有助于深入理解PDI的物理机制,对研究大功率高频电波与电离层等离子体之间复杂的非线性相互作用也有着非常重要的意义. 相似文献
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Summary On the basis of the exponential approximation for the distribution of the concentration of molecular oxygen and ozone in given parts of the ionosphere, expressions have been derived for the changes of the dissociative velocity rates of the oxygen components in the ionosphere. The numerical calculations made reveal negligible changes of these rates for heights above 100 km and sufficiently strong variations in the low ionosphere. 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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Yu. S. Saenko N. S. Natsvalyan N. Yu. Tepenitsyna 《Pure and Applied Geophysics》1988,127(2-3):335-352
A planetary model of the ionosphere and the protonosphere coupling is described. The system of three-dimensional nonstationary modeling equations of continuity and motion for the ions O+ and H+ is presented. Some numerical results of model calculations are compared with the experimental data. The important role of electromagnetic drifts in the formation of large-scale morphological peculiarities of the ionosphere and the protonosphere coupling is shown. 相似文献
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激发态氮分子N*2在电离层F区中起着重要的作用,它使F区占主导地位的O+离子的损失率增大,从而使该区的电子浓度减少. 本文利用理论电离层数值模型,通过考虑与不考虑N*2的作用,对包括1990年6月、1997年5月、1998年5月以及2000年4月磁暴事件在内的时间区间的电离层响应情形进行模拟研究,并与实测结果进行对比. 结果表明,N*2对电离层电子浓度的影响在太阳活动高年非常明显,在太阳活动低年虽有些影响,但效果并不明显,其程度远不如高年. 在太阳活动高年,不仅是磁暴期间,在较宁静期间也必须考虑N*2的影响. 而且,在考虑N*2的作用时,还与激发态振动温度Tν有关,在采用Tν=Tn（其中Tn为背景中性大气的温度）的简化处理时,所得结果与观测结果的符合程度不如对Tν进行精确计算时所得的结果好. 模拟结果还表明,太阳活动高年,N*2作用的结果主要是使150km高度以上的F区电离层电子浓度减少,而对150km以下高度的电离层电子浓度则影响不大. 另外,N*2基本不影响F2层峰高hmF2的值. 相似文献
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O. M. Lebed’ Yu. V. Fedorenko N. F. Blagoveshchenskaya A. V. Larchenko V. F. Grigor’ev S. V. Pil’gaev 《Geomagnetism and Aeronomy》2017,57(6):698-705
The phase velocities of TE and TEM waves at frequencies of 1017 and 3017 Hz, as well as the effect of precipitations during auroras on the velocities, are estimated in the Earth–ionosphere waveguide on the basis of observations of electromagnetic fields of an ionospheric source in experiments on modification of the lower ionosphere by a modulated high-power short-wave signals performed by the Arctic and Antarctic Research Institute (AARI) at the EISCAT/Heating test bench in October 2016. Probable electron density profiles in the plane-stratified ionosphere are retrieved from the numerical solution of a wave equation, which are used for the calculation of the phase velocities close to measured ones. 相似文献
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Michael L. Goodman 《Annales Geophysicae》1995,13(8):843-853
The mathematical formulation of an iterative procedure for the numerical implementation of an ionosphere-magnetosphere (IM) anisotropic Ohm’s law boundary condition is presented. The procedure may be used in global magnetohydrodynamic (MHD) simulations of the magnetosphere. The basic form of the boundary condition is well known, but a well-defined, simple, explicit method for implementing it in an MHD code has not been presented previously. The boundary condition relates the ionospheric electric field to the magnetic field-aligned current density driven through the ionosphere by the magnetospheric convection electric field, which is orthogonal to the magnetic field B, and maps down into the ionosphere along equipotential magnetic field lines. The source of this electric field is the flow of the solar wind orthogonal to B. The electric field and current density in the ionosphere are connected through an anisotropic conductivity tensor which involves the Hall, Pedersen, and parallel conductivities. Only the height-integrated Hall and Pedersen conductivities (conductances) appear in the final form of the boundary condition, and are assumed to be known functions of position on the spherical surface R=R1 representing the boundary between the ionosphere and magnetosphere. The implementation presented consists of an iterative mapping of the electrostatic potential , the gradient of which gives the electric field, and the field-aligned current density between the IM boundary at R=R1 and the inner boundary of an MHD code which is taken to be at R2>R1. Given the field-aligned current density on R=R2, as computed by the MHD simulation, it is mapped down to R=R1 where it is used to compute by solving the equation that is the IM Ohm’s law boundary condition. Then is mapped out to R=R2, where it is used to update the electric field and the component of velocity perpendicular to B. The updated electric field and perpendicular velocity serve as new boundary conditions for the MHD simulation which is then used to compute a new field-aligned current density. This process is iterated at each time step. The required Hall and Pedersen conductances may be determined by any method of choice, and may be specified anew at each time step. In this sense the coupling between the ionosphere and magnetosphere may be taken into account in a self-consistent manner. 相似文献
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通过大功率ELF/VLF调幅高频波能有效地扰动低电离层,形成等效的ELF/VLF电离层虚拟天线,用来辐射ELF/VLF波,所辐射出的低频信号可以进入中性大气层形成地球-电离层波导.本文基于调制加热模型,采用全波有限元算法计算由人工调制电离层所形成的电偶极矩所辐射出的ELF波在水平分层电离层中的波场,计算结果将与地面观测结果进行比较.模拟结果表明,所辐射出的ELF波在电离层中形成一个窄的准直波束,海面所能接收到的ELF信号强度为pT量级,并且频率越低,海面所接收到的场强就越小,与HAARP实验数据一致.结果还表明,低纬电离层对低频信号的传播衰减较大,并且所能透射出电离层的角度小,因此高纬地区更适合地球-电离层波导的激发. 相似文献