Fig. 11

Power spectrum of recorded signal 10-min snapshot. Our induction coil system having two identical back-to-back magnetic antennas aligned at N-S orientation offer a big amount of measurements at 10-min duration acquisition time intervals. Two of such snapshots are depicted in Fig. 11. Not only the measured results but also the noise and fitting curves based on nonlinear least square regression, using Lorentzian-like function, are shown. From these curves, we observed six Schumann resonance modes and their parameters that relate to resonant frequencies, Q factors, and peak powers. At the top of a and b, there is the detailed date and time of the measurement snapshot