Tests of core flow imaging methods with numerical dynamos     

Hagay Amit  Peter Olson  Ulrich Christensen 《Geophysical Journal International》2007,168(1):27-39

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Bootstrapped discrete scale invariance analysis of geomagnetic dipole intensity     

Art R. T. Jonkers 《Geophysical Journal International》2007,169(2):646-658

The technique of bootstrapped discrete scale invariance allows multiple time-series of different observables to be normalized in terms of observed and predicted characteristic timescales. A case study is presented using the SINT2000 time-series of virtual axial dipole moment, which spans the past 2 Myr. It is shown that this sequence not only bears a clear signature of a preferred timescale of about 55.6 Ka, but additionally predicts similar features (of shorter and longer duration) that are actually observed on the timescales of historical secular variation and dipole reversals, respectively. In turn, the latter two empirical sources both predict the characteristic timescale found in the dipole intensity sequence. These communal scaling characteristics suggest that a single underlying process could be driving dynamo fluctuations across all three observed timescales, from years to millions of years.  相似文献   

Ionospheric effetcs of an intense geomagnetic storm     

G. A. Mansilla 《Studia Geophysica et Geodaetica》2007,51(4):563-574

An investigation of the response of the mid-high, mid and low latitude critical frequency foF2 to the geomagnetic storm of 15 July 2000 is made. Ground-based hourly foF2 values (proportional to square root of peak electron density of F2-layer) from four chains of ionospheric stations located in the geographic longitude ranges 10°W–35°E, 60°E–120°E, 130°E–170°E, 250°E–295°E are used. Relative deviations of foF2 are considered. The main ionospheric effects for the considered storm are: long-duration negative disturbances at mid-high latitudes in summer hemisphere in sectors where the storm onset occurred in the afternoon/night-time hours; short-duration positive disturbances in the summer hemisphere at mid-high latitudes in the pre-sunset hours during the end of main phase-first stage of the recovery; small and irregular negative disturbances in the low latitude winter hemisphere which predominate during the main phase and first part of the recovery, and positive disturbances in both hemispheres at mid-high and mid latitudes prior to the storm onset irrespective of the local time. In addition, the validity of some physical mechanisms proposed to explain the F2 region behaviour during disturbed conditions is considered. gus-mansilla@hotmail.com  相似文献   

The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations   总被引：1，自引：1，他引：1  

Andrzej Krankowski  Irk I. Shagimuratov  Lubomir W. Baran  Galina Yakimova 《Acta Geophysica》2007,55(4):490-508

GPS data from the International GNSS Service (IGS) network were used to study the development of the severe geomagnetic storm of November 7–12, 2004, in the total electron content (TEC) on a global scale. The TEC maps were produced for analyzing the storm. For producing the maps over European and North American sectors, GPS measurements from more than 100 stations were used. The dense network of GPS stations provided TEC measurements with a high temporal and spatial resolution. To present the temporal and spatial variation of TEC during the storm, differential TEC maps relative to a quiet day (November 6, 2004) were created. The features of geomagnetic storm attributed to the complex development of ionospheric storm depend on latitude, longitude and local time. The positive, as well as negative effects were detected in TEC variations as a consequence of the evolution of the geomagnetic storm. The maximal effect was registered in the subauroral/auroral ionosphere during substorm activity in the evening and night period. The latitudinal profiles obtained from TEC maps for Europe gave rise to the storm-time dynamic of the ionospheric trough, which was detected on November 7 and 9 at latitudes below 50°N. In the report, features of the response of TEC to the storm for European and North American sectors are analyzed.  相似文献   

关于地球磁场极性反转机制的思索     

杨合群 《西北地质》2002,35(3):126-130

地球磁场极性在地质历史中发生过相当频繁的倒转。作者将地球内部划分为岩石圈－软流圈－中圈－液圈－固核等5个动力学圈层，认为中圈与固核间可异步旋转；地球偶极磁场由中圈与固核异步旋转时所驱动的液圈中的封闭涡流与系磁场作用产生；该偶极子场极性由地球所通过的银道面上侧或下侧磁场方向及液圈涡流的方向共同决定，二者之一反向，极性发生倒转。  相似文献   

通海地磁台(L=1.03)Pc3地磁脉动的出现率     

韩德胜  高玉芬  张福  P.J.Chi 《地震地磁观测与研究》2001,22(5):16-21

利用通海地磁台(L=1．03)1999年SMALL磁通门磁力仪记录资料，对Pc3脉动出现率的统计结果表明，日出现频次有两个峰值，即清晨06：00-07：00LT(地方时)出现频次最高，午后14：00～15：00LT为次峰值。Pc3脉动月出现频率最高的是4月和12月，其次是8月和9月；最少的是6月和7月。按季节统计结果为春秋季出现频次最高，冬季次之，夏季最低。  相似文献   

藏北羌塘盆地的航磁特征   总被引：5，自引：1，他引：5  

江民忠  王怀武 《地质科技情报》2001,20(2):95-99

将羌塘盆地的航空磁场按不同的异常面貌特征分成八大区进行了详述描述。羌塘盆地航空磁场的展布总体以东西向或近东西向为主，其次为北东向和北西向，随着向上延拓高度的增加，该特征更加明显，磁异常具有鲜明的分区性和分带性，且从北向南异常由平稳到复杂逐渐变化，这些特征是羌塘盆地特有的地质构造和磁性岩石空间组合状态的综合反映。  相似文献   

地震预报探讨中的地磁学手段   总被引：2，自引：0，他引：2  

王亶文 《国际地震动态》2001,(5):17-21

地磁手段地地震预测研究中的许多方面发挥了重要作用。在地震前兆的探讨方面占有一席之地；在探测地下构造中有许多贡献。我们可以开展许多与地震预测基础研究有关的地磁研究，例如地磁模型研究、地磁脉动研究、地球深部研究，等等。对地磁场变化规律性的研究也是提取地震地磁前兆的基础。  相似文献   

Assessment of Geomagnetic Hazard to Power Systems in Canada     

Boteler  D. H. 《Natural Hazards》2001,23(2-3):101-120

This paper presents an assessment ofgeomagnetic hazard on the five largest power systemsin Canada. From east to west these are: Nova ScotiaPower, Hydro-Quebec, Ontario Hydro West System, Manitoba Hydro, and the northern B.C. Hydro system. The aim of this study was to determine howfrequently, and where in a system, largegeomagnetically induced currents (GIC) could beexpected. To do this, an analysis was made of thespectral characteristics of the magnetic fieldvariations that cause GIC, and a review was made ofpublished magnetotelluric soundings in order todetermine conductivity models for different parts ofthe country. The magnetic field spectra and theconductivity information were then used to determinethe electric fields produced during geomagneticdisturbances. A relation was determined betweenelectric field magnitudes and the magnetic activityindex, Kp so that statistics for Kp could be used todetermine the occurrence rates of large electricfields. Power system models were used to determinethe GIC produced by the `1-year' and `10-year'electric fields experienced by each power system.  相似文献   

1945－1995地磁场功率谱及其长期变化     

王月华  谭东海 《地球物理学进展》1996,(3)

本文根据最新修正的国际地磁参考场模型，研究了１９４５－１９９５地磁场中心偶极矩变化，地磁总场及其分量Ｘ、Ｙ、Ｚ的空间功率谱，地磁场长期变化谱的经向漂移和纬向漂移的功率谱和西向漂移速度。研究中发现最近５０年偶极矩仍在继续衰减，空间功率谱的变化也呈减小趋势。在经向谱的漂移中观察到１９７０年出现最小值，而在纬向漂移变化中１９７０年出现最大值，西向漂移速度的变化也在１９７０年出现最大值，这种现象正是１９７０年发生的地磁长期变化的突变，称作地磁＂Ｊｅｒｋ＂。  相似文献