MAIN FEATURES OF THE ELECTROMAGNETIC FIELDS STRUCTURE GENERATED IN THE LOWER IONOSPHERE BY LOW-FREQUENCY GROUND-LEVEL SOURCES
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The problem of determining the electromagnetic fields generated in the lower ionosphere (50 - 500 km) by ground-level low-frequency antennas is considered.The solution is createdby the methodof normalwavesinmodelsof a sphericalEarth-ionosphere waveguide, radial inhomogeneous anisotropicionosphere, an arbitraryorientation ofthe geomagnetic field andthe electricandmagnetic dipoles. Fieldsdefinition in theionosphereathigher altitudesin thesolution instability reduces tointegration ofdifferential equationsforthe tangentialfield components ofthe penetratingon-site wave. Acombinationof differential equations forthe wave admittanceandfor the tangentialcomponentof waves is integrated atloweraltitudes. Initialconditions are given inthe WKB (Wentzel-Kramers-Brillouin)approximation.Relations betweenthe components ofthe fieldsexcitedin theionosphere bythe variousground-levelemitters are obtained using thegeneralizedreciprocity theorem.