Schumann resonance is a phenomenon associated with the occurrence of standing electromagnetic waves in the cavity between the Earth's surface and the ionosphere. The frequencies of Schumann resonance depend on several factors, including:
The main factor determining the frequencies of Schumann resonance is the size and shape of the Earth's surface and ionosphere. The Earth acts as a giant spherical resonator within which standing waves arise. Changes in the shape of the Earth or ionosphere can lead to changes in the resonant frequencies.
The conductive properties of the Earth and ionosphere play an important role in determining the resonant frequencies. The higher the conductivity, the stronger the interaction between the waves and the medium, which can affect the frequency of resonance.
The Earth's magnetic field has a significant influence on the propagation of electromagnetic waves. It can change the direction of wave propagation and, consequently, affect the resonant frequencies.
Atmospheric conditions such as temperature, pressure, and humidity can influence the conductive properties of the atmosphere and ionosphere, which in turn affects the resonant frequencies.
Solar activity, including solar flares and coronal mass ejections, can significantly alter the state of the ionosphere, leading to changes in the Schumann resonance frequencies.
Geomagnetic storms caused by the interaction of the solar wind with the Earth's magnetic field can temporarily alter the structure of the ionosphere and, accordingly, the resonant frequencies.
Although this factor is less significant, it can still have an impact. Human activities such as the use of powerful radio transmitters or the creation of large electrical networks can introduce small changes in the Schumann resonance frequencies.
All these factors together determine the precise values of the Schumann resonance frequencies, which can vary within a few Hertz.