# Progress in the Knowledge, Application and Influence of Extremely Low Frequency Signals
## 1 Introduction
There are several types of emissions that depend on the presence of rays in regions of high density plasma or plasma spherical whistles among which some are the subject of frequent study in the literature [26]. These emissions allow knowledge of the structure and dynamics of the radiation belts. Another type is choir emissions or magnetospheric choir emissions. These emissions are due to the anisotropic distribution of energy electrons within the magnetosphere [27], and it has been proven that they provide information on the region of the magnetosphere where they occur and the mechanism that generated it. Exposure to natural and especially artificial ELF electromagnetic fields (ELF-EMF), emanating from the generation, transmission, and use of electricity, is a ubiquitous part of modern life [28]. Establishing the influence of these fields has become a necessity and a topic widely studied in recent decades where most of the publications on this subject are concentrated. In 1970 the first study that tried to determine the effects of this type of field on animals, laboratory rats specifically, was published [29]. All studies carried out from that moment to the present have had and pursue the same objective: trying to determine if we are safe from the adverse effects of ELF-EMF, in order to achieve a better quality of life for current populations, as well as future populations. Different genetic changes such as cell and membrane modification, tissue damage, changes in protein conformation, modification in the absorption of different biological components, and modifications in genetic material, have been considered as possible biological effects of ELF radiation, etc. [30]. A topic of special interest is the relationship between exposure to ELF fields and the risk of development of cancer cells or carcinogenesis, as a relationship is found between said exposure and the reduction of melatonin that is involved with the possible development of cancers [31]. Research was also carried out to determine the effects of these ELF fields on the cardiovascular system [32], considering the cardiac constants by electrocardiograms (ECG). As well as the influence of the fields on the nervous system for different functional changes [33], or on the functional state of the brain by carrying out the measurement of brain activity by electroencephalogram (EEG) of different test subjects, whether animals or people [34]. The final objective of all these studies was aimed at being able to use the effects of these fields on different brain functions in order to produce controlled modulation of regional activity and become a very useful non-invasive tool for the treatment of neurological and neuropsychiatric disorders. Despite the large number of studies carried out, the relationship of the effects of exposure to ELF fields has not yielded conclusive data, most have problems related to the existence of interference, or the inability to accurately reproduce the conditions of some studies compared to others. Therefore, this issue is unresolved and needs further advanced research [35]. Currently, research on ELF waves continues in different fields from engineering, astrophysics, medicine, and even biology [36], as indicated by the large number of scientific contributions found in these areas. These contributions have doubled per decade, which implies a huge number of documents distributed within the same field of research by scientific communities. The collaboration of the authors in different thematic communities makes the progress of science more productive, since there are not only research relationships between authors but also between institutions. Science and technology are in continuous development through these collaborations, so it is necessary to establish metrics to determine the relationships between the authors.