Geomagnetic effects from expanding plasma formation of a high-altitude nuclear explosion

The geomagnetic variations on the Earth's surface due to the magnetohydrodynamic stage of expansion of the plasma formation of high-altitude nuclear explosions are considered. It is shown that the distribution of the signal amplitudes in the distances from the source obeys a certain regularity. An analysis of measurement data and numerical modeling of the magnetohydrodynamic signal confirms that the temporal shape and phases of the signal are determined by its propagation by three channels: an electromagnetic wave in the atmosphere, high-conductivity layers of the ionosphere, and the lithosphere, which possesses finite electrical conductivity. Agreement between the results of numerical modeling and measurements is obtained. A comparison of the disturbances caused by explosions and substorms indicate they are difficult to separate in the far field of the explosion.