The fundamental frequency 7.83 Hz — significance and stability

The fundamental (basic) frequency of the Schumann resonance is approximately 7.83 Hz. It is the lowest and usually the most pronounced resonance mode of the Earth-ionosphere cavity and the most frequently cited value associated with the SR.

This frequency is stable over the long term. Over the course of a day and a year it fluctuates only on the order of tenths of a hertz according to the state of the ionosphere, the distribution of storms and solar activity. The amplitude, or intensity, of the signal — that is, "how strongly" the resonance sounds — changes far more markedly than the position of the peak itself. The fundamental frequency therefore does not steadily "grow" anywhere; this is important against the widespread myth of an accelerating Schumann resonance (see #95).

The value of 7.83 Hz follows from the dimensions of the planet and the speed of light (see #7), while at the same time being lowered by losses in the real ionosphere relative to the idealized value of around 10.6 Hz (see #4 and cluster C). The stability of 7.83 Hz is well documented by long series of measurements and is one of the reasons why the SR is suitable as a reference global signal Sentman 1995Price 2016. The existence and position of the fundamental mode were predicted by Schumann's original calculation Schumann 1952.