The full-time electromagnetic modeling for time-domain airborne electromagnetic systems

In recent years, many experts dedicated their research to the forward modeling and inversion of airborne EM systems. In this paper, we carry out the modeling for ID layered media and 3D earth. We calculate not only vertical component but also the in-line component of the magnetic responses. This offers the theoretical basis for airborne EM to have multi-component survey. After comparing the impulse response and step response for airborne EM systems, we find that the impulse system response has singularity at the early time, resulting in stability problems in the EM modeling, while the step system response is non-singular, so that we can develop a stable algorithm for the calculation of the full-time EM responses for time-domain airborne systems. It is proved that the algorithm is precise and maintains well the integral/derivative relationship between the magnetic field B and the magnetic induction dB/dt. Extending the algorithm to 3D models has also obtained good results.