The Earth’s atmosphere forms the dielectric of a capacitor with the two "plates" of the capacitor being the Earth and the ionosphere. The comet's electrical disturbance will cause pressure pulses in the atmosphere before the comet arrives as well as upon arrival. It is noteworthy in this respect that a giant ionospheric disturbance accompanied the magnitude 9.3 Sumatra earthquake of 26 December 2004. The ionosphere moved up and down by about 40 km! And changes in the ionosphere have been registered 5 to 10 days before an earthquake.