Spectral analysis of geomagneticPc3 pulsations recorded at the observatories of Budkov and Belsk

Summary The numerical method of Fourier's spectral analysis is used to treat 29 pairs of samples of pc3 pulsations recorded at the observatories of Budkov (Czechoslovakia) and Belsk (Poland). The amplitude, frequency and phase characteristics of their spectra are compared. The polarization characteristics of the spectral frequency components of pulsations recorded at both observatories are compared in a quasi-stationary approximation of a plane oscillation.     

1990—1991年中国地区主磁场变化—全国地磁台站资料质量分析结果

根据全国地磁台站资料质量评审中提供的信息,对全国台站1990-1991年地磁场三分量的年均值进行了分析,给出了年变率分布特征及相应的等值线图。     

Study on noise in simultaneous geomagnetic difference data caused by the effect of S_q local-time variation

Introduction It is well known that the local geomagnetic field would change during the pregnancy of an earthquake, which may be associated with the change of the electromagnetic impedances of the crust medium. This phenomenon has been paid attention for a long time and up to now a lot of work both in observation and theory of tectonomagnetism has been carried out and much progress has been achieved (Stacey, 1964; Johnston, 1978; QI, 1977; Rikitake et al, 1980; Shapiro and Ab-dullabekov, 1982…     

Algorithm for recognizing Pc3 geomagnetic pulsations in 1-s data from INTERMAGNET equatorial observatories

The methods are suggested for analyzing the data of three-component geomagnetic observations in order to automatically recognize time anomalies-pulsations in the geomagnetic field. These methods include preliminary bandpass filtering of the data, calculating the eigenvalues of the covariance matrix of magnetic components in a moving time window, computing the generalized variance of the eigenvalues (generalization is understood as raising to a power that is distinct from the traditional power of 2), averaging the variance, and identifying the time intervals marked by the presence of pulsations by the criterion of the averaged variance of eigenvalues to exceed a certain threshold specified by the fuzzy-logic methods.     

太原基准地震台地磁背景噪声分析

太原基准地震台数字化地磁观测项目建成运行后,背景噪声水平较大,影响观测资料的使用.采取多种技术措施,认为地电阻率观测对地供电是地磁稳频干扰的主要成分,是地磁背景噪声的一项重要干扰因素.     

On the geomagnetic lunar variation at Istanbul

Summary The article describes lunar daily magnetic variation inH, D andZ components of the earth's magnetic field at Istanbul. Maximum occurs at 10.03 l.hr. (lunar hour) in theH component, 3.38 l.hr. in theD and 2.15 l.hr. in theZ component, during the period 1949 to 1968. Also, the seasonal variation of the lunar magnetic variation has been determined and it is seen that the variation of the phase inD andZ are opposite from the phase of the lunar variation inH, and the amplitudes of the lunar variation inH, D andZ are greatest during the northern solstice.     

Results of monitoring the geomagnetic variations at the Magadan and Paratunka observatories

We analyze the magnetic tensor and tipper data in the interval of periods from a few minutes to a few hours for the geomagnetic time series of 2007–2008. The frequency responses, the polar diagrams, and the real and imaginary induction arrows which reflect the effects of geoelectric heterogeneities are calculated. The monitoring of the tipper and tensor data series revealed the annual variations in these parameters, which are caused by the changes in the electric conductivity of the lithosphere. The anomalous variations identified in the behavior of the magnetic tipper and tensor are probably due to earthquakes with M ≥ 6.3.     

基于数学形态学的地磁数据噪声处理软件

在当前地磁数据噪声预处理过程中,存在效率低下、处理质量因人而异的缺点,借鉴数学形态学的去噪方法,基于C/C++编程语言和Qt开发框架,设计开发一套地磁数据噪声处理软件,提高地磁数据预处理工作的自动化水平。由重庆地震台网的应用效果可知,该软件具有较为广泛的应用前景。     

Study on noise in simultaneous geomagnetic difference data caused by the effect of Sq local-time varlauon

A new concept is suggested on tectonomagnetic research about the noise in simultaneous geomagnetic difference data caused by the effect of S _q local-time variation, together with the method of theoretical calculation. The level of the noise and its contribution to the total noises of the differences data are analyzed. The result indicates that the noise increases linearly with the increase of the distance between the two stations in the range of 40° longitude-difference, and its increasing rate is about 0.4 nT/(°) at latitude 40°N. The example calculated at a pair of sites with longitude-difference 0.357°, shows that the noise is about one fifth of the total noises of the difference data on geomagnetic quiet-day. Contribution No. 06FE3008, Institute of Geophysics, China Earthquake Administration.     

Estimation of effect of unequal secular variation on geomagnetic data reduction

The geomagnetic field components are periodically measured at repeat stations. The main objective of the repeat stations is to provide data for tracing the secular variation of the geomagnetic field components. Secular variation at the repeat station is generally different from that at geomagnetic observatory used in the data reduction. The effect of the secular variation differences on geomagnetic data reduction was estimated for the regions of Europe, North America (below 60°N) and Australia, respectively, during the period of 2000-2010. These estimations were obtained by using the monthly mean values of north, east and vertical components of geomagnetic field, recorded at geomagnetic observatories. The effects were calculated by using observatories pairs, with distances from 350 km (in Europe) to 3100 km (in North America and Australia). The maximal effects were found to be the smallest in east component in Europe and North America, and vertical component in Australia; the effects increase with time from a central reduction epoch and they are not constant during mentioned eleven years; they were less than 1 nT only in Europe, for distances between the observatories up to 1000 km in all three components and for periods spanning ±1 month from a central epoch. It was found that their year to year variability is mostly due to the non-eliminated external field residuals in the observatories monthly means; their effect is up to 3 nT for ±3 months from a central epoch. Further, the real effects were compared to those modeled by IGRF-12 model. The maximal differences between the real and the modeled values are below 4.5 nT in all three components, for ±3 months from a central epoch.     

On the origin of seasonal variation of aerosol optical thickness in UV range over Belsk,Poland

Aerosol optical thickness (AOT) and seasonal variation of AOT over Belsk, Poland, in the UV wavelength range (310–380 nm) have been analysed using results of measurements by Brewer spectrophotometer No. 064 and Cimel sunphotometer data for the 2002–2007 period. The comparison of AOT derived from direct Sun measurements by Brewer spectrophotometer in the 310–320 nm range and retrieved from Cimel measurements at longer wavelengths shows good correlation (R = 0.96), with overestimation of retrieved values compared to the measured ones by about 6%. Basing on aerosol microphysical properties taken from almucantar retrievals and Mie theory, optical properties of aerosol in the UV range has been calculated. Analysis of seasonal variation of AOT at Belsk reveals two maxima: in April and July–August. Analysis of back-trajectories in conjunction with analysis of fire maps from Fire Information For Resource Management System shows that these seasonal maxima are connected with seasonal biomass burning in Eastern and Southern Europe.     

向家坝-上海特高压直流输电线路对地磁观测环境影响的试验研究

在向家坝上海±800 kV特高压直流输电线路2010年6月全电压全功率带电调试期间,进行多测点同步地磁观测试验.结果表明,只要直流线路在极导线上或大地里存在电流,就会对地磁观测产生影响,引起地磁垂直分量Z和水平分量H产生台阶型变化,且垂直分量Z影响更大.     

Study on terrestiral noise in data of geomagnetic total field in North China

The terrestrial noise in the differencial data of geomagnetic total field recorded at 21h in North China was fitted by using the geomagnetic vector data from Beijing Observatory. The terrestrial noise level and its spatial feature in this region was discussed. A method, which may be useful for justifying the quality of fitting, was provided in this paper. The analysis indicates that the terrestrial noise is one of the important noise in tectonomagnetic study. It is shown that the susceptibility effect is quite small and the orientation effect is the main component in the terrestrial noise in North China. The rough spatial feature of the magnetic anomaly in crustal substance was infered from the spatial feature of terrestrial noise. The measurement precision and the source noise level of data at 21h in this region were obtained in the analysis of residual noise. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 441–447, 1993.     

基于虚拟日变台进行地磁矢量数据日变通化方法

流动地震地磁矢量观测是一种获取地震前兆异常的方法,试验研究和观测实例表明,地震孕育引起的地磁场异常变化量级较小,因此在观测、数据处理过程中都要尽可能消除误差提高精度.本文主要从地磁矢量数据日变通化精度方面开展讨论,首先使用反距离加权插值法由泰安、武汉、崇明、杭州4个地磁台观测资料计算出蒙城地磁台相应的虚拟地磁数据,其磁偏角、水平分量、垂直分量三个要素与真实观测值的相关系数分别高达0.9987、0.9946和0.9806,验证了反距离加权插值方法对地磁观测数据空间插值的有效性.其次,选择东部和西部测区分别使用反距离加权插值方法建立各地磁矢量测点位置的虚拟日变台并用其进行通化,实例计算结果表明,该方法可有效提高日变通化精度,对于地磁台站稀疏地区更具实际应用价值.     

地磁观测数据重构技术研究

基于地磁相对记录数据在1 000 km范围内有较高的相关性,本文以缺失数据台站的邻近台站作为参考台站,通过关系拟合及加权对缺失数据进行了重构.数据仿真结果表明:重构数据与原始数据的变化形态极为一致,磁静日平均重构残差仅为0.11 nT,磁扰日平均重构残差为0.23 nT;重构数据与原始数据的功率谱密度变化特征基本相同,相关性高达1.0.此外,从时域和频域上验证了空间加权法在地磁相对记录数据重构上的有效性,将其应用于实际缺失数据重构中也取得了较好的效果.      

中山站高频雷达回波的日变化特征及地磁活动的影响

利用新建中山站高频雷达2010年4月到2011年2月的观测数据,研究了中山站高频雷达回波的日变化特征以及地磁活动的影响. 研究结果表明,中山站高频雷达回波具有明显的日变化特征且受地磁活动影响较大. 雷达回波发生率的峰值在地磁活动较小时处于日侧;随着地磁活动的增强,峰值减小并向夜侧移动. 另外,平均多普勒视线速度具有明显的昼夜分布,夜侧主要为正向速度,即朝向雷达,日侧主要为负向速度,即远离雷达;随着地磁活动的增强,平均回波强度和平均多普勒视线速度的峰值都会增加,而多普勒谱宽则会减小.     

地磁场长期变化和日长十年尺度变化的周期特征

根据历史地磁场模型GUFM1、第10代国际参考地磁场（IGRF10）模型和日长资料,采用小波变换方法,分析了地磁场磁矩、能量、西向漂移等参数的长期变化和日长十年尺度变化的周期分量及其时变特征.结果表明,1800～2005年期间,偶极子磁场长期变化有82年和48年准周期分量,它们与日长变化的周期没有直接关系.非偶极子磁场参数的长期变化与日长变化有66年和32年准周期分量,66年准周期比32年准周期强.在66年准周期分量,西向漂移比日长变化超前8.8年,非偶极子磁场能量比日长变化滞后15.6年.日长十年尺度波动和地磁场长期变化的起源不存在因果关系.     

中山站高频雷达回波的日变化特征及地磁活动的影响

利用新建中山站高频雷达2010年4月到2011年2月的观测数据,研究了中山站高频雷达回波的日变化特征以及地磁活动的影响. 研究结果表明,中山站高频雷达回波具有明显的日变化特征且受地磁活动影响较大. 雷达回波发生率的峰值在地磁活动较小时处于日侧;随着地磁活动的增强,峰值减小并向夜侧移动. 另外,平均多普勒视线速度具有明显的昼夜分布,夜侧主要为正向速度,即朝向雷达,日侧主要为负向速度,即远离雷达;随着地磁活动的增强,平均回波强度和平均多普勒视线速度的峰值都会增加,而多普勒谱宽则会减小.     

不同磁通门经纬仪产出基线值对比分析

选取中国地磁台网中6个地磁台站基线值对比分析.结果表明,两套绝对观测仪器对同一分量所定出的两条基线,在经过墩差和仪器差改正之后,仍不能完全重合,D、H、Z三分量的基线值差值存在明显的起伏变化.初步判断,造成两套仪器基线值差值变化的原因很可能为两仪器所在墩差的变化,也就是说,在同一个观测区的不同点位,地磁场的差值也在不断变化.     

On the variation in the geomagnetic dipole over the geological history of the Earth

The global database on the paleointensity, containing determinations of the virtual dipole moment (VDM) for a stable (normal) regime of the geomagnetic field in a time interval of up to 3.5 Ga, is supplemented by new VDM determinations and analyzed. The field generation process started no later than 3–3.5 Ga (earlier data are absent) at the stage of the Earth’s core formation. Since that time, the dipole value has differed from its present value by no more than an order of magnitude, and the deviations that have already been detected tend toward smaller values. The distribution of VDM values in the time interval 0–400 Ma is bimodal, which apparently reflects the presence of two different generation levels of the geomagnetic field distinguished by a relatively large value (close to the present field value) and a relatively small value (approximately half as large as the present value). The total duration of decreased VDM values appreciably exceeds that of increased VDM values (179.1 and 28.6 Myr, respectively). On the whole, data on the paleointensity do not contradict the hypothesis about the dipole nature of the field over the last 400 Myr; however, the number of determinations at high paleolatitudes is too small to draw decisive conclusions on the validity (or invalidity) of the dipole field approximation based solely on paleointensity data.