Study On The Characteristic Of Ground And Ionosphere Electromagnetic Fields Excited By Underground SLF/ELF Radiator

The abnormal phenomenon of the electromagnetic radiation before the earthquake getsthe more and more attention of the seismologists, and it has been verified by manyearthquake examples. The earthquake electromagnetic radiation is the information directlycoming from the earthquake source, and it is a very important precursor means of theearthquake short-term and imminent forecasting. The frequency spectrum of theelectromagnetic radiation mainly concentrates in the super low frequency (SLF) andextremely low frequency (ELF) bands. At present, the generation mechanism andfrequency spectrum characteristic of the electromagnetic radiator are not still extremelyclear during the earthquake breeding period. Only the frequency components below verylow frequency (VLF) can seep the ground, and can be received by the receiving apparatuson the ground because the stratum is a highly lossy medium. So the relevance of theearthquake radiator and the underground SLF/ELF radiator is very big. But in order to putthe monitored electromagnetic radiation to the earthquake prediction and forecasting, itneeds to solve the following several key problems:①Whether is the electromagneticradiation the abnormity?②Where does the electromagnetic radiation come from?③How much is the electromagnetic radiation larger than the normal background?In order to solve above several key problems, the detailed studying process of thisdissertation is as follows: Firstly, in order to ascertain the possible position of theunderground radiator from the measured SLF/ELF electromagnetic information on thegroundsill and in the space, the propagation characteristic of the electromagnetic fieldsexcited by the underground SLF/ELF radiator on the ground and in the space must bestudied. Because the wavelength of the electromagnetic wave is very long, and the lengthof the antenna is less than the wavelength, the radiator can be idealized as an electricdipole. Because the stratum is a high absorption and attenuation medium, and it is known by the trapped surface wave propagation theory that the electromagnetic field intensityexcited by an underground horizontal electric dipole (HED) is much larger than thatexcited by an underground vertical electric dipole (VED), the underground SLF/ELFradiator can be idealized as a HED. It is calculated by idealizing the ground and theionosphere, and it is contrasted with the actually measured data to ascertain the position ofthe underground SLF/ELF radiator. Secondly, it needs to know the statistical distributionrules of the atmospheric noise along the day and night, the seasons and the regions inorder to distinguish the received electromagnetic signal to be the background interferenceor the abnormity. The mainly studying contents of this dissertation are as follows:1. The propagation characteristic of the fields excited by the SLF/ELF radiator on thegroundsill in the isotropic earth-ionosphere waveguide has been analyzed and studied. Ithas been studied for many years in SLF frequency band by the domestic and foreignscholars, and it has both the theories and the experiments, and it has been obtained theconfirmation. But the algorithms applied in the SLF frequency band are only used to theELF frequency band by the domestic and foreign scholars. In the dissertation, two kinds ofalgorithms have been proposed, namely the speeding numerical convergence algorithmand the numerical integral algorithm, which are not only suitable for SLF frequency bandbut also suitable for ELF frequency band. Moreover, the theoretical calculation has alsobeen made. The results indicate that it has not only confirmed the existing SLF algorithms,but also provided the good studying foundation in order to further study the characteristicof the ground and the ionosphere electromagnetic fields excited by the undergroundSLF/ELF radiator.2. The propagation characteristic of the fields excited by the underground SLF/ELFradiator in the isotropic earth-ionosphere waveguide has been analyzed and discussed, andSchumann resonance has also been confirmed. Formerly it mainly aims at theunderground emergency communication of the long wave. Because the propagationdistance is short, and the depth of the radiator is fairly shallow, the model of the plane halfspace is used. In the dissertation, it is based on the relevance of the earthquake radiatorand the underground SLF/ELF radiator. The SLF/ELF radiator is idealized as thehorizontal electric dipole, and the ground and the ionosphere are idealized, and it isanalyzed and calculated by the spherical model. The spatial distribution rules of theelectromagnetic fields in the whole earth-ionosphere waveguide have been obtained bycomparing with the traditional method. Because the expressions of the ground and theionosphere electromagnetic fields excited by the underground SLF/ELF radiator are theform of the spherical harmonic series, and their calculation is not only complex but alsothe speed is very slow, a speeding numerical convergence algorithm has been proposed in the dissertation, which is suitable for the SLF/ELF frequency band under the non-idealelectric conductor condition. The results indicate that the analysis and the calculation canbe fast and effectively carried on by this algorithm. The accuracy of this algorithm has notonly been confirmed, but also the theory of the lateral wave has further been confirmed.3. The spatial distribution rules of the fields excited by the underground ELF lineradiator in the isotropic earth-ionosphere waveguide have been studied. It may be the sumof the fields excited by the underground ELF point radiator. The spatial field intensitydistribution of the electromagnetic fields excited by the underground ELF single linearradiator and two linear radiators has been calculated and discussed, respectively, and thestrong and weak distribution of the spatial field intensity values is expressed by the colorcode.4. The propagation characteristic of the fields excited by the underground SLF/ELFradiator in the isotropic and anisotropic ionosphere has been respectively analyzed anddiscussed. The stratum, the atmosphere and the ionosphere are seen as a whole to bestudied in the dissertation. The whole propagation process of the electromagnetic fieldsexcited by the underground deeply buried SLF/ELF radiator from the stratum and theatmosphere to the satellite has been analyzed and studied. The limitation of the traditionalpartition research has been improved, and it has been enhanced to comprehensively knowand grasp the propagation mechanism and the spatial distribution of the SLF/ELFelectromagnetic wave. Moreover, the invertibility of studying the propagation mechanismand the spatial distribution of the SLF/ELF electromagnetic wave has been established.5. Statistical distribution rules of the global SLF/ELF atmospheric noise have beenanalyzed and predicted by analyzing the Antarctic observed data and unifying the overseaspublicly published literatures and unpublished AD reports retrieved and collected in thedissertation as well as the statistical distribution rules of the global VLF atmosphericnoise.