Observations of geomagnetic pulsations and variations with a new borehole magnetometer down to depths of 3000 m

b
A triaxial magnetometer has been developed for investigating the in situ skin effect of horizontal geomagnetic pulsations and variations in deep boreholes. The observations were carried out in the pilot borehole of the Continental Deep Drilling Program of Germany (KTB) down to depths of 3000 m and up to temperature of 90 C. A weak skin effect, due to the known very low conductivity of the penetrated crystalline rocks, of 90 to 95 per cent in amplitude and -5 to -10 rotation in phase has been observed at periods of 10 s and magnetometer depth of 2400 m.
An essential prerequisite for all calculations is the accurate determination of the orientation of the downhole magnetometer. It is demonstrated how oriented record samples of temporal variations at depth correlate precisely with those from the surface.
Results from surface magnetotelluric (MT) investigations show strong local distortions of the telluric field. The distortion of the MT tensor response has been determined by means of newly introduced skin-effect transfer functions, which are assumed to be undistorted.     

全球增暖的另一可能原因初探

太阳是地球流体(大气和海洋等)运动的最终能量源,地球环境,尤其是气候的变化不能不与太阳活动有关.目前,普遍将全球增暖归结为温室气体含量增加所导致的温室效应的加剧,这无疑是有一定依据和有道理的.但从科学上来讲,人类活动所引起温室气体增加的影响,并非是唯一原因.基于已有的一些研究结果,从太阳活动的观点所进行的初步分析表明,太阳活动也可能是引起近世纪全球增暖的另一个重要原因.太阳活动的影响主要包括太阳辐射的直接影响和引发地磁场变化的间接影响两个方面,地球磁场的变化将可通过动力过程和热力过程而影响大气环流和气候的变化.     

地磁台网高压直流输电判别处理系统设计

介绍地磁高压直流输电干扰自动判断处理系统的主要功能、架构设计和运行流程,并对其核心功能的实现过程进行描述。本系统为全国地磁观测人员处理高压直流输电干扰提供具体时间、幅度参考标准,有利于地磁预处理数据质量的提高。     

Centennial to millennial geomagnetic secular variation

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.     

Study on electric variations of media in epicentral area by geomagnetic transfer functions

ＳｔｕｄｙｏｎｅｌｅｃｔｒｉｃｖａｒｉａｔｉｏｎｓｏｆｍｅｄｉａｉｎｅｐｉｃｅｎｔｒａｌａｒｅａｂｙｇｅｏｍａｇｎｅｔｉｃｒａｎｓｆｅｒｆｕｎｃｔｉｏｎｓＸｉａｏ－ＰｉｎｇＺＥＮＧ；（曾小苹）Ｙｕｎ－ＦａｎｇＬＩＮＩ；（林云芳）Ｚｈｏｎｇ－ＪｉｅＺＨ...     

西太平洋暖池两柱样沉积物的磁性地层学研究

根据西太平洋暖池WP92-5,WP92-3柱样沉积物的磁性地层学研究结果,发现WP92-5柱样沉积物的磁性记录了3个地球磁场漂移(地球磁场极性反转),即Gothenburg,MonoLake(或Rubjerg)和Mungo(或Maelifell),其界限年龄分别为12.5kaB.P.,24.0(23)kaB.P.和31.0(28—31)kaB.P.;WP92-3柱样沉积物的磁性也记录了前两个地球磁场漂移。这一结果表明,西太平洋暖池区对35kaB.P.以来地球磁场极性发生的3次短暂的漂移有明显的响应。由于两柱样都采集于赤道附近南半球暖池区,其磁倾角的变化有一定的特殊性。     

用曲面插值方法建立海洋局部地磁场模型

地磁场模型是地磁场的数学表达式,国内外已有多种建立地磁场模型的方法,对于局部地磁场模型来说,应用比较多的是多项式方法和曲面样条函数方法。讨论了基于曲面样条函数建立局部地磁场模型的原理和方法,并在实测数据基础上对模型的精度进行了验证。