REGISTRATION AND MODELING OF ULF-ELF SIGNALS AT STARAYA PUSTYN STATION DURING THE FENICS-2019 EXPERIMENT
1 Institute of Applied Physics, Russian Academy of Sciences 2 Space Research Institute, Russian Academy of Sciences 3 Radiophysics Research Institute of Lobachevsky Nizhny Novgorod University 4 Schmidt Institute of Physics of the Earth, Russian Academy of Sciences 5 St. Petersburg Branch of Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation Russian Academy of Sciences 6 Geological Institute FRC “Kola Science Center of the Russian Academy of Sciences”
Journal: Science and technological developments
Keywords: controlled source, electromagnetic field, ionosphere, waveguide propagation
Аnnotation: In September 2019, on the Kola Peninsula, an experiment was carried out to generate ULF-ELF signals at night using two decommissioned industrial power lines as a horizontal emitting antenna. The line current was supplied from an external 200 kW generator. The current strength varied from 240 A at low frequencies (0.382 Hz) to 20 A at the highest (194 Hz). The paper presents the results of recording ULF signals at the Staraya Pustyn magnetic station, which is 1610 km away from the transmission line. Signals with frequencies from 0.6 Hz to 6.4 Hz were recorded. The signal amplitudes, normalized to the emitter current, varied in the range of 0.4-0.7 fT/A. For theoretical estimates, two models were used: 1) formulas from the theory of ELF field excitation in the Earth-ionosphere waveguide and 2) a numerical model of the ULF field in the atmosphere and ionosphere created by a linear surface current of infinite length. The numerical model is based on the calculation of the Maxwell system of equations in a vertically inhomogeneous atmosphere and ionosphere, the parameters of which are calculated using the IRI model. A fundamental feature of model 2 is that it takes into account the contribution of the ionospheric waveguide propagation to the excited field at large distances at frequencies above the critical waveguide frequency ~0.5 Hz. The dependence of the amplitude of the recorded signals of an artificial source on the frequency in the range of 2-8 Hz has a non-monotonic character, which may be a manifestation of the effects of waveguide propagation along the ionosphere.