Study Of The High-Altitude Nuclear EMP By Using A Novel Integral Method

High-altitude nuclear electromagnetic pulse(HEMP)usually has narrow band-width,large peak value,and widespread.It can propagate to thousands of kilometers far away from the burst point.Thus,HEMP is harmful to various military and civil electronic devices,and detailed research on the HEMP becomes critical to the protection and reinforcement of electronic devices and facilities.In this thesis,the basic knowledge of the current source of the HEMP and the nonself-consistent electromagnetic model(Karzas and Latter's model)are first introduced.Then the self-consistent electromagnetic model(OWM,outgoing wave method)is introduced.The disadvantage of the two methods is that they can only deal with the simulation of the HEMP in one-dimensional symmetric space.Due to the limitations of the method of difference in the large 3-dimensional spatial domain and for the research of the HEMP under nonlinear asymmetric conditions,a novel integral method(IM)is introduced in the thesis.The results calculated by the IM and the OWM are shown and compared,and the good performance of the IM model was observed.This thesis provides a novel approach for the research of the HEMP under complicated asymmetric conditions.Here are the main work and innovations of this thesis.Firstly,the corresponding space-time decomposition and basis function decomposition of the deposition region are introduced in the retarded time domain.These decompositions are not only based on the spatial domain but also based on the retarded time domain,which means the decompositions move simultaneously with space and time.Essentially,these decompositions are methods of exchanging computer memory for reducing computing time.Using this method in the low-order and high-order integral methods introduced in this thesis can significantly reduce the amount of computing time needed for the numerical simulation while without much loss of accuracy.Secondly,the novel integral method(IM)is introduced to solve the simplified Maxwell's equations under the planar approximation of the gamma-ray source(which is also a zero-order method).In this part,the space-time domain decomposition and the basis function decomposition are introduced,and the numerical equations are derived,under the planar approximation of the gammaray source.After these,the HEMP and the current source calculated are shown,and the results are compared and discussed,which shows that the IM and the OWM are equivalent.The characteristics of the HEMP,such as the peak value,the bandwidth,the saturation effect,and the boundary conditions of the deposition region,are discussed.Thirdly,a relative complicated integral method(second-order IM)is introduced to solve Maxwell's equations under the spherical approximation of the gamma-ray source.Under this condition,the zero-order method is not appropriate anymore,and the second-order method is needed here.The space-time domain decomposition,the basis function decomposition,and the current fitting are shown under the spherical approximation of the gamma-ray source.The HEMP and the current source calculated are shown,and the results are compared and discussed,which shows that the IM and the OWM are equivalent.Meanwhile,the characteristics of the HEMP,such as the peak value,the bandwidth,the saturation effect are discussed.Fourthly,a fifth-order integral method is introduced to simulate the HEMP under asymmetric situations.A simplification of the integral equation is introduced to improve the simulation efficiency.After this,the fifth-order method is introduced to simulate the current source distribution in the deposition region.The space-time decomposition and the basis function decomposition are the same as under the spherical approximation of the gamma-ray source,and the numerical equations are derived here.In the end,the results of the numerical simulation are shown,and the high-frequency method,often utilized in the numerical simulation of the HEMP,are discussed and verified.Fifthly,the results and examples shown in this thesis verify that in addition to the gamma yield on the line of sight(LOS),the gamma yield distribution in the region nearby the LOS will also influence the HEMP propagating onto the ground.Thus,under some asymmetric situation,the oftenused one-dimensional methods(OWM)and low-order IM are not adequate anymore,whereas the high-order IM can handle those problems.