The modeled tadpole that fits the observed one shown in Fig. 3. Upper panel shows a time evolution of the mass density at the detection point (spikes source), where L_P  −  L_D = 8.33 Mm. Middle panel shows the corresponding wavelet power spectrum with the tadpole pattern (characteristic period P = 6.3 s) outlined by contour at the 99% confidence level. Bottom panel shows the global wavelet spectrum (black line) with the maximum for the period P = 6.3 s. The gray line indicates the 99% significance level.