Model disturbance of Schumann resonance by the SGR l806-20 γ-ray flare on December 27, 2004

A possible effect is modeled and discussed on the Schumann resonance records of the giant γ-ray flare from SGR 1806-20. We show that the dayside ionosphere modification is able to cause an abrupt reduction in the power spectra of global electromagnetic resonance. Spectral modifications fade in time, so that the usual and regular patterns are recovered in tens of minutes. An application of signal sonogram is suggested for the signal processing around the time of γ-ray burst, which would facilitate detection of the event.