Earth_TLM repository

Abstract

The interest in the study electromagnetic propagation through planetary atmospheres is briefly discussed. Special attention is devoted to extremely low frequency fields in the Earth’s atmosphere for its global nature and possible applications to climate studies. In the Earth’s case, the system can be considered as a spherical electromagnetic resonator in which two concentric and large conducting spheres with a radius around 6300 km are separated by a very small distance of around 100 km, the Atmosphere’s height. A numerical solution using the Transmission Line Method is proposed. The classical spherical-coordinate description is easy to use, however, the important difference in the dimensions along the three coordinate directions causes high dispersion in the numerical results. A Cartesian scheme is proposed to reduce this dispersion difficulty. A pre-processing stage is the key point introduced to reduce the high demand of memory and time calculation and make the solution feasible. A parallelized Fortran code together with pre- and post-processing Python programs to ease user interface are provided with this work. Details on the Fortran code and the Python modules are included both in the paper and the source codes to allow the use and modifications by other researchers interested in electromagnetic propagation through planetary atmospheres. The program allows calculation of the time evolution of the electromagnetic field at any point in the atmosphere. It includes the possibility of considering multiple time-dependent sources and different homogeneous and inhomogeneous conductivity profiles to model different situations. Profiles to study day-night asymmetries or locally perturbed profiles which have been attributed to earthquakes in the literature are implemented, for instance.