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1.
用气—水—土3层模型分析海水中水平电偶极子源的电磁场分布 总被引：1，自引：0，他引：1
由空气－海水－海底３层模型求得了海水中水平电偶极子源的电磁场分布,与以往不考察空气层的两层模型的电磁场分布相比,它更接近于实际分布情况。文章还对不同海底电导率时水平电偶极子源的电场水平分量进行了数值计算和分析。 相似文献
2.
阐述了在以电磁场探测海底电特性的方法中应用人工电磁场源的必要性;建议用水平电偶极子作为人工电磁场源的天线;介绍了两种物理模型的分析结果;讨论了增加探测海底深度的可能途径。 相似文献
3.
阐述了在以电磁场探测海底电特性的方法中应用人工电磁场源的必要性;建议用水平电偶极子作为人工电磁场源的天线;介绍了两种物理模型的分析结果;讨论了增加探测海底深度的可能途径。 相似文献
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海流运动因切割地磁场会生成微弱的电流,从而在海洋及其周围空间中激发感生电场.本文基于海流感应电磁场微分方程及其边界条件,推导了水平地层正弦洋流感应电场表达式.建立海水层、海底沉积层以及地壳绝缘层构成的地电模型,模拟计算正弦洋流感应电场及感应电流密度,分析海水层和海底沉积层中感应电流分布特征,并讨论了影响洋流感应电场的因... 相似文献
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海水是一种高电导率的流体,根据电磁感应定律,运动的海水切割地磁场会在海水中产生感应电流,从而产生感应电磁场。本文从麦克斯韦方程出发,推导出一维速度场海水运动感应电磁场偏微分方程,利用电磁场水平分量在海表面和海底面上的连续性条件,得到海水运动感应电磁场表达式,并编写了Fortran计算程序。计算了常速度海水运动感应电磁场,并与格林函数法计算结果进行了对比,两种方法的计算结果一致。计算了变速度(即海水运动速度随深度变化)海水运动感应电磁场,并讨论了海水运动周期和海底介质电导率对海水运动感应电磁场的影响。计算结果表明:海水运动周期和海底介质电导率对常速度海水运动和变速度海水运动感应电磁场都有影响,但影响程度不同。在本文所述模型和参数条件下,海水运动感应电场和感应磁场振幅分别可达6μV/m和10nT,这与海洋大地电磁响应的量级相当。因而在处理海洋大地电磁数据时,海水运动感应电磁响应是不可忽略的噪音干扰,需要采用必要的压制手段。 相似文献
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7.
南黄海海水中悬浮体的研究 总被引：34，自引：10，他引：34
本文通过对海水中悬浮体样品的过滤、分析及结合海水透光度测量,得出了1983年11月和1984年7月海水中悬浮体的平面分布和垂直分布模式,即:水平分布有三个高含量区和两个低含量区,黄河及长江的现代输入物质对中部深水区基本上没有影响;垂直分布出现明显的层化现象,11月份,在密度跃层下缘出现悬浮体跃层。本区悬浮体含量和成分,具有陆间海的过渡性特征。悬浮体的主要来源是海底沉积物的再悬浮,其次是河流输入物和浮游生物。海浪是影响悬浮体分布的主要因素。潮流加强了海浪的作用,并与海流一起,将掀起的物质搬运他处。海底地形在一定条件下,控制了海浪作用的临界深度。黄海中部冷水团影响了悬浮体的水平扩散和垂直扩散。 相似文献
8.
早期的海啸监测系统主要依赖地震监测网或海底压力计阵列网,但都存在诸如建设和维护成本高、监测范围有限等问题。对海啸的实际观测和模拟发现,广泛分布的海底电缆能够反映海啸运动产生的感应电磁场,由此发展出了更为便捷和经济的海啸感应电磁场监测方法。本文介绍了海啸感应电磁场的理论推导过程、不同海啸速度模型,以及对不同海底地形类型的海啸感应电磁场解析解的研究进展。对比分析海啸感应电磁场的电压、扰动磁场、矢量电磁场三种海啸电磁监测方法的优缺点后认为,矢量电磁场监测具有测量海啸传播方向的优势,利用矢量电磁测量结合现有的海啸监测系统能更快更准更实时地预警海啸。 相似文献
9.
海水是一种高电导率的流体。不停运动的海水因切割地磁场而产生感应电流,从而产生感应电磁场。本文从麦克斯韦方程出发推导了地磁场三分量作用下一维海流感应磁场表达式,并分析了地磁场水平分量对海流感应电磁场的影响。计算表明地磁场水平分量的影响随纬度变化。在高纬度地区地磁场水平分量对海流感应电磁场影响很小,而在低纬度地区它会对海流感应电磁场产生明显的影响。本文还分析了变化的海水电导率对海流感应电磁场的影响。 相似文献
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基于2020年夏季的大面航次观测数据,分析了烟台—威海北部海洋牧场及邻近海域海水溶解氧浓度垂向分布最小值（氧最小值层）的空间分布特征,并探讨了影响因素。从6月至8月,海水溶解氧浓度不断减小,垂向结构亦存在显著变化。海水溶解氧浓度垂向分布的最小值主要集中于7月的近岸海域,最小值大致从外海向近岸方向减小,其距离海底高度及与底层溶解氧浓度之差的绝对值均于双岛湾邻近海域为最大。海水溶解氧浓度垂向分布的最小值位于最强密度层结以下。但是海水溶解氧浓度垂向分布最小值的强度向北减小,而密度层结向北增大,两者的空间分布基本相反,说明密度层结抑制垂向湍流扩散可极大减少深层海水溶解氧的来源,是海水溶解氧浓度垂向分布最小值形成的必要条件,但不是主导因素。在海水溶解氧浓度垂向分布的最小值层,表观耗氧量存在垂向分布的最大值,大部分站点的pH存在垂向分布的最小值,说明局地增强、持续的生物地球化学耗氧是控制海水溶解氧浓度垂向分布最小值形成和空间分布的一个重要过程。研究结果表明氧最小值层是夏季烟台—威海北部近岸海水溶解氧垂向结构的典型特征之一。 相似文献
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用矩阵对角化方法求解了在各向异性分层介质中水平电偶极的辐射问题 ,并引入“过渡矢量”,利用其传播特性求得定解 ,此方法简单实用 ,不要求相似变换矩阵归一化。作为应用 ,具体计算了电离层被加热产生的极低频源在几千公里范围水下不同深度远处接收场强的量级 相似文献
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N. A. Palshin A. A. Nozdrina V. A. Matyushenko A. M. Porai-Koshits I. V. Egorov 《Oceanology》2006,46(3):325-334
A technique for studying near-shore currents is assessed that is alternative to the traditional methods. The technique is based on the measurements of anomalous electromagnetic fields induced on land in the near-shore zone. The method of coastal electromagnetic monitoring was tested in the central part of the Zimnii Coast of the Gorlo of the White Sea. The results of numerical modeling of electric fields induced by tidal currents allowed us to obtain theoretical estimates of the expected signal and to choose the site of the measurements and the optimal parameters of the receiving lines applied. The experimental studies were performed on the Zimnii Coast of the Gorlo of the White Sea using two horizontal receiving lines, one of which was located on the coast and the other ran in the sea. These studies provided experimental estimates of the electric field of the tides in the Gorlo of the White Sea, which agreed with the theoretical evaluations. The results of the studies proved the efficiency of the method of coastal electromagnetic monitoring, which may be used in order to study tidal, offset-onset (surge), and quasi-stationary currents. An important advantage of the electromagnetic methods lies in the possibility to perform the studies throughout the year, including the winter period. 相似文献
13.
为了研究起伏海面对雷电电磁传播的影响,本文利用Barrick表面阻抗理论和Wait近似算法,采用改进二维分形海面模型模拟起伏海面,利用数值模式,分析起伏海面的雷电电磁传播特征,并进一步讨论了起伏海面对时差法闪电定位系统定位精度的影响。结果表明:起伏海面对垂直电场和磁场的峰值的影响不显著,但会引起波形的上升期时间的延长,浪高越大,影响越明显;随着观测距离的增加,雷电垂直电场波形的上升时间逐渐变长;风速的变化与雷电垂直电场波形的上升时间成正比;由于海面起伏引起雷电电磁场波形在传播中的变化会影响基于时差法闪电定位系统的定位精度,定位误差可达几至十几公里。 相似文献
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An active source electromagnetic sounding system for marine use 总被引：2，自引：0，他引：2
M. C. Sinha P. D. Patel M. J. Unsworth T. R. E. Owen M. R. G. Maccormack 《Marine Geophysical Researches》1990,12(1-2):59-68
Instrumentation has been developed for carrying out active source electromagnetic sounding experiments in the deep oceans. Experiments of this type are directly and uniquely sensitive to the presence of molten or partially molten material, to temperature structure and to the porosity of upper crustal rocks such as those that accommodate hydrothermal circulation systems. Electromagnetic sounding experiments therefore represent an extremely desirable addition to the existing range of geophysical techniques for studying geological processes in thermally, hydrothermally or magmatically active regions—for example, at oceanic spreading centres.The instruments can be operated in regions of rugged, unsedimented sea bottom terrain, and are designed for investigating the distribution of electrical conductivity within the oceanic crust and uppermost mantle. The instrumentation consists of a deep towed, horizontal electric dipole transmitter and a set of free-fall, sea bottom, horizontal electric field recording devices.The transmitter is a deep-towed instrument, which is provided with power from the towing ship through a conducting cable. The transmitter package is fitted with an integral echo sounder, which allows it to be towed safely a short distance above the seabed. Electromagnetic signals are transmitted from a neutrally-buoyant antenna array, which is streamed behind the deep tow.The sea bottom receiving instruments each consist of a recoverable package which contains the instrumentation and digital recording system, an acoustic release unit, four low-noise, porous electrodes arranged in two orthogonal, horizontal dipoles, and a disposable bottom weight.The instruments have been used at sea on three occasions. On their most recent use, active source signals were successfully recorded during an experiment to investigate crustal magmatism and hydrothermal circulation beneath the axis of the East Pacific Rise. 相似文献
15.
根据麦克斯韦电磁理论,在地磁场中运动的海水将产生感应电磁场。利用一个简单的数学物理模型对感应电磁场在海水内部的分布进行了计算,结果表明海浪产生的电磁场明显依赖于海浪波动的周期及浪高。在100 m的海水深度内,海浪产生的磁感应强度的大小为纳特数量级,而电场强度的大小为几个微伏每米。在同一海水深度处,磁感应强度随海水波动的周期呈现近线性变化,而电场强度的大小有一个极值,该极值随海水深度的增加向长周期方向移动。海浪产生的电磁场是影响海洋电磁探测数据精度的主要噪声之一。 相似文献
16.
Measurements of the natural extremely low-frequency (ELF) radio noise (known as Schumann resonances) in the period 1988-1989 have enabled average atmospheric noise levels and Schumann resonance parameters to be deduced. At 45 Hz, the average measured electric field was 41.6 dB·μV/m·√(Hz). It is assumed that the Schumann resonance noise field in the air-space in the vicinity of the observation point can be considered to be represented as the sum of four components, one arising from propagation over a short great-circle path, and a second representing a long great-circle path contribution, each of these having an upgoing and a downgoing part. The noise fields can then be estimated at any given depth below the ground (or sea) surface from the measured values in the air. The authors present results showing the computed fields produced in the sea from submerged horizontal electric quadrupole and vertical electric dipole man-made sources, and compare these with the subsurface atmospheric noise fields deduced from the experimental measurements 相似文献
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The paper considers the propagation of the electromagnetic fields having a range of tens of cycles per second in a horizontally-inhomogeneous ocean. The TM-wave characteristics in the presence of a horizotal conductivity jump are estimated. The amplitudinal and phase values of the electric intensity's vertical component are provided for various conductivities of a two-segment sea of constant depth. A conclusion is made that marine environment inhomogeneities can he studied through electromagnetic techniques.Translated by V. Puchkin. 相似文献
18.
本文分析赤道西太平洋的考察资料，结果表明：气象要素的变化具有典型的热带和赤道气候特征。受埃尔－尼诺事件的影响，气象特征变化显著。降水天气过程的出现、海表水温和气温的水平分布有明显的规律。天气状况对海表水温无明显影响。一些气象特征与邻近热带和赤道海区不同。 相似文献
19.
A. S. Zapevalov 《Izvestiya Atmospheric and Oceanic Physics》2009,45(2):253-261
The effect of sea surface waves longer than Bragg components on the backscattering of centimeter electromagnetic radiation is studied on the basis of data on direct field measurements of sea-surface slopes. A situation in which waves with wavelengths greater than 10 cm are longer than the Bragg components is considered. The increase in the backscattering cross section that is due to the presence of long waves is numerically estimated for sounding at horizontal and vertical polarization. Nonlinear effects in the field of surface waves result in the departure of the distribution of sea-surface slopes from a Gaussian distribution and lead to a change in the backscattering cross section. At a sounding angle of 35°, this change may reach 15% with respect to the cross section calculated for a Gaussian surface. 相似文献
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运用微扰法研究了平面波入射分层介质粗糙面的电磁波透射问题,采用改进的一维分形海面模型模拟实际的分层海面,推导出了平面波入射时的透射系数计算公式.通过数值计算得到了HH极化透射系数随散射角的变化曲线,讨论了中间介质介电常数和厚度、摩擦风速和入射波频率对透射系数的影响,得到改进的一维分形分层海面透射系数的基本特征、分区特征和随频率变化的特征,结果表明透射系数近似具有"量子化"特征. 相似文献