Time domain simulation of electromagnetic cloaking structures with TLM method

This paper was published in Optic Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OE.16.006461The increasing interest in invisible cloaks has been prompted in part by the availability of powerful computational resources which permit numerical studies of such a phenomenon. These are usually carried out with commercial software. We report here a full time domain simulation of cloaking structures with the Transmission Line Modeling (TLM) method. We first develop a new condensed TLM node to model metamaterials in two dimensional situations; various results are then presented, with special emphasis on what is not easily achievable using commercial software.This work has been supported in part by the “Ministerio de Educación y Ciencia” of Spain under research projects No. FIS2004-03273 and FIS2007-63293 cofinanced with FEDER funds of the European Union

A 3D TLM code for the study of the ELF electromagnetic wave propagation in the Earth's atmosphere

The interest in the study of 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 monitoring studies among others. In the Earth's case, the system can be considered as a spherical electromagnetic shell 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 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 numerical dispersion in the results. A Cartesian scheme with equal node size for all directions is used to reduce this undesired dispersion. A pre-processing stage is the key point introduced to lessen the resulting 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 the 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.MCIN/AEI 10.13039/501100011033 (grant PID 2020-112805 GA-I00)Grant PID 2020-112805 GA-I00 funded by MCIN/AEI/10.13039/ 50110001103

Schumann resonance data processing programs and four-year measurements from Sierra Nevada ELF station

In this work, we present to the scientific community the measurements taken during four years, from March 2013 to February 2017 inclusive, by the Extremely Low Frequency Sierra Nevada station, Spain, together with the data processing programs developed in Python (version 3.8) to extract the Schumann resonance (SR) parameters (i.e., amplitudes, resonant frequencies, resonance widths) in 10 min time periods from these records. The measure- ments correspond to the voltage induced by the atmospheric electromagnetic field at the north-south and east- west oriented magnetometers of the station. The process comprises four stages. The spectrum, calibrated in the frequency band ranging from 6 Hz to 25 Hz, is obtained at the first stage using the Welch method with Hann windows. The second step eliminates the anthropogenic noise generated by different undesired sources. Next, a non-linear fit of the measured spectrum combining Lorentzian functions together with a linear term is carried out in order to identify the presence of SRs and quantitatively characterize them. This third step is carried out using the Python package Lmfit, which implements the Levenberg-Marquad algorithm. Finally, a compact and easy-to- read output is generated at the fourth stage, using the power of the Numpy arrays and the npz format. In addition, four Jupyter notebooks with the description of the code and the possibility of their use in interactive mode are presented as supplementary material with this paper

Nuevas aportaciones a la interacción de ondas electromagnéticas transitorias con estructura conductoras

Tesis Universidad de Granada. Departamento de Física Aplicad

Long Term study of the Schumann Resonance Regular Variations Using the Sierra Nevada station ground-based magnetometers. Data

We present the data of a study of the Schumann Resonance (SR) regular variations (March 2013 – February 2017) using the ground-based magnetometers from the Sierra Nevada station, Spain (37◦02’N, 3◦19’W). The study is based on the fitting parameters obtained by the Lorentzian fit, calculated for each 10-min interval record, namely, peak amplitudes, central frequencies, width of the resonances and the power spectrum integral for the first 3 SR modes. We consider three time-scales in the study: seasonal, monthly and daily variations. The processed data collected by the Sierra Nevada station are also made public with this work

Notebooks to study the Schumann Resonance regular variations

This folder is an additional material to the PhD thesis "Analysis of the Sierra Nevada ELF station recordings: a contribution to the study of the Schumann Resonances". It contains a wide range of computational tools that allow the researchers to obtain, export, visualize and study all the information related to the SR parameters. These computational tools are presented in the form of a collection of Jupyter notebooks. The data (the SR parameters extracted from the Sierra Nevada ELF station) are also contained in the folder

A 3-D TLM code for the study of the ELF electromagnetic wave propagation in the Earth’s atmosphere

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

On the need of a unified methodology for processing Schumann resonance measurements. Data collection

Dataset of the paper "On the need of a unified methodology for processing Schumann resonance measurements" published in JGR Atmospheres