A 5000 year geomagnetic palaeosecular variation record from western Canada     

Gillian M. Turner 《Geophysical Journal International》1987,91(1):103-121

  相似文献   

Geo-effectiveness of solar wind extremes     

Hari Om Vats 《Journal of Astrophysics and Astronomy》2006,27(2-3):227-235

Examples of extreme events of solar wind and their effect on geomagnetic conditions are discussed here. It is found that there are two regimes of high speed solar wind streams with a threshold of ∼ 850 km s^-1. Geomagnetic activity enhancement rate (GAER) is defined as an average increase in Ap value per unit average increase in the peak solar wind velocity (Vp) during the stream. GAER was found to be different in the two regimes of high speed streams with +ve and-ve IMF. GAER is 0.73 and 0.53 for solar wind streams with +ve and -ve IMF respectively for the extremely high speed streams (< 850 km s^-1). This indicates that streams above the threshold speed with +ve IMF are 1.4 times more effective in enhancing geomagnetic activity than those with -ve IMF. However, the high speed streams below the threshold with -ve IMF are 1.1 times more effective in enhancing geomagnetic activity than those with +ve IMF. The violent solar activity period (October–November 2003) of cycle 23 presents a very special case during which many severe and strong effects were seen in the environment of the Earth and other planets; however, the z-component of IMF (Bz) is mostly positive during this period. The most severe geomagnetic storm of this cycle occurred when Bz was positive.  相似文献   

地磁场强度变化对暴露年代测定的影响及校正     

邵庆丰  陈仕涛 《海洋地质与第四纪地质》2007,27(1):87-93

在103-105a的尺度上,地磁场强度变化是影响陆地宇生核素生成速率的主要因素,其影响程度取决于样品的地理位置和暴露时间。根据已有的磁场古强度数据,模拟200 ka以来海拔2 km、25°N和40°N的地表10Be生成速率的变化,进而分析地表宇生核素生成速率变化对岩石暴露年代测定的影响及其模式年龄的校正。校正磁场强度变化后,海拔2 km、25°N上,50-200 ka的模式年龄可被压缩14%~19%,大于1σ的误差,相同海拔40°N上的模式年龄可减小约8%。对中低纬两组模式年龄的校正充分证明,磁场强度引起的陆地宇生核素生成速率变化是暴露年代测定中主要误差源之一,尤其在低纬高海拔地区这一影响更不容忽视。  相似文献   

基于IGS超级跟踪站的近实时GPS气象研究及应用   总被引：1，自引：0，他引：1  

张双成  叶世榕  刘经南  张斌 《测绘科学》2008,33(2):93-95

目前国内许多城市开始将CORS综合应用网服务于气象部门,为给地基GPS气象研究人员提供一个真实的研究环境,本文基于IGS超级跟踪站网络搭建了一个近实时GPS气象系统,并结合实测数据验证了该系统的有效性。基于该平台可以系统地研究GPS遥感水汽、层析水汽三维分布、数值天气预报同化GPS水汽以及利用电离层分布进行空间天气预报等理论。  相似文献   

Centennial to millennial geomagnetic secular variation     

M. Korte  C. G. Constable 《Geophysical Journal International》2006,167(1):43-52

A time-varying spherical harmonic model of the palaeomagnetic field for 0–7 ka is used to investigate large-scale global geomagnetic secular variation on centennial to millennial scales. We study dipole moment evolution over the past 7 kyr, and estimate its rate of change using the Gauss coefficients of degree 1 (dipole coefficients) from the CALS7K.2 field model and by two alternative methods that confirm the robustness of the predicted variations. All methods show substantial dipole moment variation on timescales ranging from centennial to millennial. The dipole moment from CALS7K.2 has the best resolution and is able to resolve the general decrease in dipole moment seen in historical observations since about 1830. The currently observed rate of dipole decay is underestimated by CALS7K.2, but is still not extraordinarily strong in comparison to the rates of change shown by the model over the whole 7 kyr interval. Truly continuous phases of dipole decrease or increase are decadal to centennial in length rather than longer-term features. The general large-scale secular variation shows substantial changes in power in higher spherical harmonic degrees on similar timescales to the dipole. Comparisons are made between statistical variations calculated directly from CALS7K.2 and longer-term palaeosecular variation models: CALS7K.2 has lower overall variance in the dipole and quadrupole terms, but exhibits an imbalance between dispersion in   g ¹₂  and   h ¹₂  , suggestive of long-term non-zonal structure in the secular variations.  相似文献   

2001年三次6级左右地震前西昌地磁的虚假异常研究   总被引：1，自引：0，他引：1  

牟雅元  王天国 《地震研究》2002,25(3):246-250

2001年，在西昌地磁台300km范围内连续发生了三次6级左右地震；即2月23日在西昌北200km的四川雅江县境内发生的6．0级地震；5月24日在西昌西南140km的盐源县内境内发生的MS5．8地震，10月27日在西昌西南260km的云南永胜发生的MS6．0地震。震前，西昌地磁台各相对观测记录分量和绝对观测量都发生了明显的异常变化。研究结果表明，由于邻近基建施工，使观测环境发生改变，引起大幅度虚假异常，这些异常 尽管与三次地震对应较好，但不是先兆异常。  相似文献   

国际地磁参考场在我国地磁基础研究中的应用     

王文 《国际地震动态》2002,(5):4-6,7

国际地磁参考场资料在我国得到广泛应用。利用国际地磁参考场资料，我国学者研究了高斯分析、地球磁场模型及其源场可能位置、重磁关系、核幔耦合、地磁场能量、地球非偶极子磁场西向漂移等。在绘制中国地磁等值图中也利用了某些国际地磁参考场资料。  相似文献   

Determining the magnetic field in the core–mantle boundary zone by non-harmonic downward continuation     

L. Ballani  H. Greiner-Mai  D. Stromeyer 《Geophysical Journal International》2002,149(2):374-389

  相似文献   

A model of the geomagnetic field and its secular variation for epoch 2000 estimated from Ørsted data     

Nils Olsen 《Geophysical Journal International》2002,149(2):454-462

  相似文献   

The time-averaged magnetic field in numerical dynamos with non-uniform boundary heat flow   总被引：2，自引：0，他引：2  

Peter Olson  U. R. Christensen 《Geophysical Journal International》2002,151(3):809-823

  相似文献