Basic quantities: frequency, amplitude, Q-factor

Each Schumann mode is described by three basic modal parameters: frequency (the position of the peak), amplitude or intensity (how strongly the mode "sounds") and the Q-factor (sharpness, width of the peak). Together these three quantities characterize the state of the resonator and of the excitation.

Frequency gives the position of the resonance peak in the spectrum — for the first mode ~7.83 Hz. The amplitude (intensity) expresses the energy in the given mode and fluctuates considerably more than the frequency, because it directly reflects the instantaneous global lightning activity. The Q-factor (quality factor) measures the sharpness of the resonance: a high Q means a narrow, "clean" peak, a low Q a broad and damped one. For the first Schumann mode Q \approx 4-6, so it is a strongly damped resonance with broad peaks.

The field is very weak: the magnetic component B reaches on the order of a few picotesla (pT) per mode and the electric component E on the order of hundreds of nanovolts per meter (nV/m) Tatsis 2024. Such low levels require sensitive magnetic coil and electric antennas and careful suppression of interference Tatsis 2024. These basic quantities form the framework within which the SR is measured, modeled and interpreted Sentman 1995Price 2016.

*Cluster A file — part of the Schumann resonance knowledge base.*