Analysis of the Influence of Underground Media on the Ground Field Characteristics in Low Altitude Explosion Source Areas

Study the numerical simulation results of electromagnetic pulses (SREMP) in low altitude explosion source areas on different ground points under the action of different underground media (seawater, freshwater, dry soil, and wet soil). We adopt the Finite Difference Time Domain (FDTD) method based on the rotating ellipsoid hyperbolic orthogonal coordinate system, taking into account the intense changes in the source and field near the explosion center. Non uniform step sizes are used in both space and time, and the spatial grid is set as an exponential function. The time step size is set by CFL conditions, and the OpenMP parallel algorithm is used to improve computational efficiency. The calculation results show that different underground media have different effects on the field values of the same monitoring point on the ground in the source area. Under the action of freshwater, the electromagnetic field strength of the monitoring point changes more prominently with distance, and the farther the distance, the higher the freshwater electromagnetic field value. From the peak field strength graph of ground monitoring points changing with distance, it can be seen that there is a significant difference in the peak electric field of seawater compared to the other three media. The waveform characteristics of the electric field of seawater and dry soil are the closest, while the waveform characteristics of the magnetic field of seawater and wet soil are the closest. The research provided an algorithmic basis for the simulation calculation of ground monitoring points in the low altitude nuclear explosion source area, and provided theoretical support for the analysis of long-distance ground detection of low altitude nuclear explosions.