Generation of Geomagnetic Disturbances in the Ionosphere by a Tsunami Wave

The mechanism of the generation of the geomagnetic field disturbance accompanying tsunami wave propagation is considered. Electric currents in the marine environment and the ionosphere are the source of the disturbance. The current in the marine environment arises as a result of its motion in the tsunami wave, while the current in the ionosphere occurs due to the occurrence of an acoustic-gravity wave (AGW) propagating from the atmosphere on the ionosphere. The source of the AGW is the vertical displacement of the surface of the marine environment during tsunami-wave propagation in it. Although the ionospheric conductance is significantly smaller than the conductivity of the marine environment, the current value in it may considerably exceed the current value in the marine environment due to the exponential growth in the AGW amplitude during AGW upward propagation. The spatial distribution of a disturbance in the induction of the magnetic field of electric currents flowing in the marine environment and in the ionosphere is obtained with allowance for their mutual inductance. It is shown that the generation of the ionospheric electric current considerably changes the characteristics of the geomagnetic field disturbance induced by a tsunami wave. Calculations have demonstrated the possibility of space monitoring of tsunami waves with the use of satellites to record disturbances of the geomagnetic field.