Numerical Simulation Of The Finite Difference Of Transient Electromagnetic Field In The Rectangular Loop Of Air-ground System

Transient electromagnetic method in mineral resources prospecting,hydrogeology survey of promoted step by step,but in the region of the terrain fluctuation or mountain bad traffic environment greatly restricted the application of transient electromagnetic method.Therefore,the development of TEM can effectively solve the above problems.At present,most of the researches on domestic aviation transient electromagnetic or semi-aeronautical(ground-to-air)transient electromagnetic method are still in the initial stage,which requires a lot of forward modeling.In this paper,the finite difference method is used to simulate the three-dimensional numerical simulation of the large loop air system.In this paper,starting from the Maxwell equations of electromagnetic places meet,first of all,the method of using dipole synthetic solving homogeneous half space overspending: broken moment and the analytical solution of vertical magnetic field,and with its as the initial value,directly calculate propagation process of the secondary field in underground medium;Second big loop source was deduced the three dimensional forward difference iterative equation,using the non-uniform grid subdivision for space,can greatly reduce the number of grid subdivision,save computation time,adopt the method of adaptive for discrete time.Will forward modeling results and the analytical solution of uniform half space comparison shows the three dimensional simulation results conform to the requirements of the precision,the layered model and 1 d forward modeling results contrast,found that three-dimensional layered model and one dimension error of the result is the same in the previous high,then gradually reduced,the late rise again.In addition,the effects of different flight heights on transient electromagnetic signals and the changes of vertical magnetic field intensity at different observation points were observed.Designed several groups of typical model to carry on the numerical simulation,and the calculation results to choose more classic moment map slices of vertical magnetic field,can be clearly observed in the transmission of electromagnetic field in different time underground.Then some models use translation algorithm to calculate the apparent resistivity of the whole area.In this paper,the research mainly around the above several aspects launches the research,the research work for air transient electromagnetic method in actual production to provide theoretical guidance,verify the large loop source transient electromagnetic method is feasible,empty for transient electromagnetic 3-d inversion research foundation.