Fig. 3
From: ULF impulsive magnetic response at mid-latitudes to lightning activity
The example of two-pulses pattern observed on 10/04 22:07:26.4 LT (stroke moment is marked by a vertical dashed line) at MOS. The upper panels show waveforms of H (left-hand) and D (right-hand) components, and bottom panels show the relevant wavelet spectra. Time-averaged wavelet spectra are shown in the right-hand bottom panel. Right-hand upper insert shows the map with direction towards a source.