Dipole source and conversion problem in transient electromagnetic sounding
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摘要: 偶极子源是电磁法研究的基本对象，是构成更复杂探测装置与资料解释的前提，也是电磁法勘探技术开发与创新的理论基础。从偶极子源的概念出发，导出了均匀大地表面上的主要偶极子源瞬变电磁场公式，并指明正垂直阶跃脉冲与负垂直阶跃脉冲激发的瞬变电磁场公式的异同，以加深认识。举例说明了相应于电性源与磁性源的场分量可根据电磁场的互易定理相互转换，便捷推导公式。重点阐述了由偶极子源的场强公式运用叠加原理可衍生更复杂的电磁场公式，诸如大回线源及其任意一点的瞬变电磁场公式，盘活了瞬变场的应用。Abstract: The dipole source is the basic research object of electromagnetic method and the precondition for constitution of more complex detection devices and data interpretation, and also the theoretical basis for the development and innovation of technology. In this paper, starting from the concept of dipole source, the main transient electromagnetic field formulas of the dipole source of uniform earth surface are introduced or derived, and the similarities and differences between transient electromagnetic field formulas for positive and negative vertical step pulse excitation are indicated to deepen theoretical understanding. It illustrates that the electrical field components corresponding to the electrical and magnetic source can be converted to each other according to the reciprocity theorem of electromagnetic field, convenient for derivation formula. The paper described emphatically that more complicated formulas of electromagnetic field can be derived from the field intensity formulas of the dipole source by using superposition principle, such as transient electromagnetic field formulas for a large loop and any points, the application of the transient field is activated.
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