天然电磁场激励下球体的天然电场选频法异常成因分析

在以往实践应用的基础上，主要从均匀半空间内球体模型的角度研究天然电场选频法异常的成因.首先从自然因素和人文因素2方面分析天然电场选频法的场源问题；从麦克斯韦方程组出发，利用边界条件求取谐变磁场作用下，均匀半空内导电导磁球体在地表主剖面上感应二次电场的解析计算式；根据拉普拉斯方程和边界条件，获得谐变电场作用下，均匀半空间导电球体在地表主剖面上的异常电场水平分量计算式；对理论模型的各个参数进行假定，计算三维谐变磁场、谐变电场作用下，地表主剖面上良导球体的水平电场异常曲线.通过对模拟计算结果分析可知，在水平谐变磁场和谐变电场共同作用下，获得的地表电场异常曲线与野外实测结果形态相似、特征相同.

Study on the anomaly genesis of the frequency selection method for a sphere under natural electromagnetic field

On the basis of the past practice on the application, the purpose of this paper is to study the anomaly genesis of the frequency selection method for a sphere in homogeneous half space. First of all, from two aspects of natural factors and human factors analyse the natural electric field method of frequency selective source problem. Based on the Maxwell equations and the boundary conditions, the analytic expressions of an induced electric field outside the conductive magnetic sphere are obtained for a sphere under harmonic magnetic field in homogeneous half space. According to Laplace equations and boundary conditions, the horizontal component of anomaly field on the surface is obtained for a conductive sphere under harmonic electric field in homogeneous half space. Parameters of models are assumed, profile curves of total electric field on the ground are calculated for a conductive sphere under three dimensional harmonic electromagnetic fields. Theoretical simulating curves are compared with the practical exploration curves, and similar characteristics are indicated when the sphere under horizontal harmonic magnetic fields and stray electric fields in homogeneous half space.