地球弓激波前的低频磁流体波     

李少峰  孙炜 《地球物理学报》1990,33(2):239-241

一、引言 在地球弓激波前存在着低频磁流体波。这种低频磁流体波是太阳风在地球弓激波上的反射粒子和太阳风粒子之间相互作用产生的。根据人造卫星的观测资料可以得到,在地球弓激波前,Pc3-4脉动频率范围内的低频磁流体波的主频率和行星际磁场强度  相似文献   

涡旋诱发重联模型（Ⅰ）——动力学特性   总被引：2，自引：1，他引：2       下载免费PDF全文

刘振兴  濮祖荫 《地球物理学报》1990,33(1):1-11

本文首先从理论上系统地研究了涡旋诱发重联的基本动力学特性.包括:涡旋诱发重联的物理机制;Kelvin-Helmholtz（K-H）不稳定性和撕裂模不稳定性耦合过程;磁流体涡管的基本特性;不同尺度涡旋间的相互作用,动能和磁能间的转化及准稳态时流线、磁力线、等涡度线和等电流密度线的相似性等.用二维MHD数值模拟方法研究了上述一些特性,并与理论分析结论进行了比较.结果表明,模拟结果证实了理论推论.涡旋诱发重联是产生局部磁场重联的重要机制之一,该模型在磁顶区的应用将另文发表.  相似文献   

夹皮沟金矿田成矿模式     

王光奇  武贵禄 《吉林地质》1991,10(4):45-54

本文以岩性—构造—事件法论述了夹皮沟金矿田地质演化历史,并建立了夹皮沟金矿田成矿模式,对金矿田成矿理论和金矿预测提出了新的见解。研究认为,该矿田金的物质来源具多源性,金矿形成具多期多阶段性。区内北西向弧形韧性剪切带是金的主要控矿构造。总结出该矿田具有“一型三式”的特点,即花岗—绿岩型,包括板庙子式、大线沟式和三道岔式。  相似文献   

DIAGNOSTIC STUDY FOR INTRASEASONAL OSCILLATION OF THE MIDDLE-HIGH LATITUDES IN A LOW RESOLUTION GLOBAL SPECTRAL MODEL     

Zhang Qin  Ni Yunqi  Lin Wuyin  Wang Zhaomin  D. D. Houghton 《Acta Meteorologica Sinica》1991,5(4):411-425

In this paper, five-year simulated data from a low-resolution global spectral model with triangular trunca-lion at wavenumber 10 are analyzed in order to study dynamical features and propagation characteristics ofintraseasonal oxillations over the mid-latitudes and the tropical atmosphere. The simulations show that thereis the 30-50 day periodic oscillation in the low-resolution spectral model without non-seasonal external forcing,and spatial scale of the intraseasonal oscihations is of the globe .Further analysis finds that propagation charac-ters of intraseasonal oscillations over the mid-latitudes and the tropics are different. The 30-50 day oscillationover the tropics exhibits structure of the velocity potential wave with wavenumber 1 in the latitudinal and thecharacter of the traveling wave eastward at speed of 8 longitudes/day. However, the 30-50 day oscillationsin mid-latitude atmosphere exhibit phase and amplitude oscillation of the standing planetary waves and theyare related to transform of teleconnection patterns over the mid-latitudes. The energy is not only transferredbetween the tropics and the middle-high latitudes, but also between different regions over the tropics. Based on the analysis of 5-year band pass filtered data from a 5-layer global spectral model of Jow-ordetwith truncated wavenumber l0,investigation is done of the source of intraseasonal oscillations in the extratropicalmodel atmosphere and its mechanism. Results show that (1) the convective heat transferred eastward alongthe equator serves as the source of the intraseasonal oxillation both in the tropical and the extratropical atmos--phere; (2) the velocity-potential wave of a zonal structure of wavenumber 1 gives rise to oxillation in divergentand convergent wind fields of a dipole-form as seen from the equatorial Indian Ocean to the western Pacificduring its eastward propagation, thus indicating the oscillation in the dipole-form heat soure:e/sink pattertl; (3)the tropical heat-source oscillation is responsible for the variation in phase and intensity of the extratropicalstationary wave train, and the interaction between the oscillating low-frequency inertial gravity and stationaryRossby modes that are probably mechanisms for the oscillations ip the middle-high latitudes.  相似文献   

30—60天大气振荡的全球特征   总被引：14，自引：6，他引：14       下载免费PDF全文

李崇银 《大气科学》1991,15(3):66-76

利用ECMWF格点资料,分析研究了大气季节内(30—60天)振荡的全球特征。30—60天振荡动能的分布表明高纬度地区要比赤道地区大得多。说明那里有较突出的30—60天振荡。中高纬度地区的30—60天振荡与热带有明显不同,垂直结构为正压模态,以纬向2—4波为主,多为向酉传播。30—60天振荡存在明显的低频遥相关,北半球主要为欧亚—太平洋(EAP)型和PNA型,南半球主要有澳洲—南非(ASA)型和环南美(RSA)型,并且在全球范围构成南北半球相互衔接的低频波列,即EAP-ASA波列和PNA-RSA波列。南北半球30—60天大气振荡有明显的相互影响,本文研究了南北半球30—60天振荡相互影响的3种主要过程。  相似文献   

应用于复合型脆断的综合断裂理论     

李波扬 《武汉大学学报(信息科学版)》1991,(1)

现有的复合型裂纹扩展断裂准则大多只考虑了裂纹尖端附近某一点处的某个力学参量。本文同时考虑了正应力、剪应力及塑性区的影响,并在此基础上提出了一个新的复合型断裂理论——综合断裂理论。同近年来的实验数据进行比较,得到了与实验十分接近的结果,并且还解释了其它理论所不能解释的实验现象。  相似文献   

类透镜介质中的传导模及与激光束的耦合     

翁兴涛 《武汉大学学报(信息科学版)》1994,(4)

从求解柱坐标内亥姆霍兹方程出发，导出了类透镜介质传导模的特征参量、场分布状态及传播常数，求出了入射激光束和导模之间的耦合系数，并讨论了它们的物理意义．  相似文献   

傅利叶重建法的数值模拟研究     

王亚秀 《内陆地震》1994,8(4):310-314

运用ＣＴ技术中的傅利叶重建法，根据任意所给的两个初始速度模型，用几组平行射线束进行扫描，采集走时数据，并利用走时数据反演速度图象．反演结果与初始模型比较两者基本相符合。由此证明，傅利叶重建法在一定条件下可以用来反演地壳速度结构，并可得到较好的结果．这种方法是ＣＴ技术应用于地学研究的一种新的尝试．  相似文献   

菲涅耳积分计算公式及其应用     

曹庆源 《武汉大学学报(信息科学版)》1986,(2)

菲涅耳积分是物理光学、微波技术与天线等多学科共用的特殊函数,其形式为上限可变而又不能积出的两个定积分,通常将其按变量u的不同区间分别用正或负幂级数计算。本文在原有公式的基础上研究出了简单、精密且变量复盖实数域的计算公式及其计算机程序。内容包括:(1) 最佳分区点u_1的选择;(2) u≤u_t时菲涅耳积分的变比级数表达式;(3) u>u_1时菲涅耳积分的三角函数表达式;(4)程序流程图;(5) 抽样运行数据及检验结果。  相似文献   

Bacterial contribution to sedimentary organic matter; a comparative study of lipid moieties in bacteria and Recent sediments     

H. Goossens  W. Irene  C. Rijpstra  R.R. Düren  J.W. De Leeuw  P.A. Schenck 《Organic Geochemistry》1986,10(4-6)

A systematic study of the lipid composition of thirteen bacterial species and three Recent sediments (methanogenic sediment, cyanobacterial mat and evaporative gypsum crust) was undertaken in an attempt to recognize bacterial organic matter in sediments. A sequential method, which distinguishes between three different modes of occurrence of lipid moieties (free, OH⁻- and H⁺-labile), was applied. The acid-labile fractions are discussed.The three main groups of bacteria, archaebacteria, gram-positive eubacteria and gram-negative eubacteria, are easily distinguished. Methanogenic and extremely halophilic archaebacteria are characterized by the presence of diphytanyl glyceryl ether and the absence of fatty acids. The gram-positive eubacteria contain primarily iso- and anteiso-branched fatty acids whereas the gram-negative bacteria and sediments are dominated by β- and α-hydroxy fatty acids. A wide variety of H⁺-labile hydroxy fatty acids was observed which included several, as yet unknown, structures.β-Hydroxy fatty acids in this H⁺-labile mode of occurrence are exclusively present in bacteria. Their distribution patterns in sediments are considered “fingerprints” of past and present bacterial populations. The specific differences in β -hydroxy fatty acid compositions observed in the different bacteria and the three sediments investigated, suggest that amide-linked β-hydroxy fatty acid patterns are useful as markers of bacterial populations and therefore of environmental conditions.  相似文献