Electricity-related phenomena such as lightning are observed both in cloudy and clear conditions. These atmospheric electric fields, or atmospheric electric potential gradient, relate to the Earth's negative surface charge and the ionosphere's positive charge, representing a potential difference of approximately 300 kV. These effectively form a huge condenser, together with the atmosphere between the two poles that behaves as a dielectric insulator that transmits electrostatic activity.
Ion production from sunlight and other sources means that the atmosphere is not a perfect insulator, and electrical currents flow continuously. This continuous potential difference mechanism may be related to the fact that worldwide lightning activity acts as a generator, forming a global electrical circuit between the ionosphere and the Earth's surface.
Local atmospheric electric fields fluctuate significantly due to atmospheric phenomena such as wind, rain, snow, fog, haze and lightning. Thunderclouds in particular are strongly ionized, resulting in remarkable electric field fluctuations. Research has been conducted on this effect to predict lightning.
In calm conditions, electric fields are minimally affected by such meteorological phenomena.
Long-term observation data indicate seasonal and interannual electric field changes during calm conditions, which may relate to variations in atmospheric electrical conductivity. Condensation nuclei associated with atmospheric pollution and other factors may be a factor.
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