Examples of natural low frequency electromagnetic waves include Very Low Frequency (VLF) and Extremely Low Frequency (ELF) waves. These waves have frequencies below 30 kHz for VLF and below 300 Hz for ELF. Here are a few examples and their uses:
Schumann resonances: These are a set of ELF frequencies that occur naturally in the Earth's electromagnetic environment. They are generated by the global lightning activity, which excites the resonant cavity between the Earth's surface and the ionosphere. Schumann resonances are primarily studied for scientific purposes and have also been linked to some biological effects.
Solar-terrestrial interactions: The Sun emits a broad range of electromagnetic radiation, including VLF and ELF waves. These waves are involved in interactions between the solar wind and the Earth's magnetosphere, such as magnetospheric oscillations and auroral activity. Studying these waves helps in understanding space weather and its potential effects on various technological systems.
Geophysical phenomena: Natural phenomena like thunderstorms, earthquakes, and volcanic eruptions can produce low frequency electromagnetic waves. These waves are studied to gain insights into the underlying geophysical processes and to develop methods for detecting and monitoring these events.
Regarding the dangers of exposure to VLF and ELF waves, the scientific consensus is that low frequency electromagnetic waves in these ranges do not pose significant health risks to humans at typical environmental exposure levels. These waves have low energy and are generally not able to penetrate deeply into biological tissues.
However, it's worth noting that there are certain man-made sources of electromagnetic fields, such as power lines and certain industrial equipment, which can generate ELF fields at higher levels. Prolonged exposure to intense ELF fields from these sources has been associated with potential health concerns, although the evidence is not conclusive and is still a subject of ongoing scientific research.
As with any form of electromagnetic radiation, it is always important to follow relevant safety guidelines and regulations to minimize unnecessary exposure to electromagnetic fields and ensure the safe operation of equipment.