Kosteusrevontulet

Kosteusrevontulet, which translates to "moisture aurora" or "wet aurora," is a colloquial Finnish term for a natural phenomenon that can sometimes be mistaken for the Northern Lights. Unlike the true aurora borealis, which is caused by charged particles from the sun interacting with the Earth's atmosphere, Kosteusrevontulet is a weather-related optical illusion. It typically occurs during foggy or misty conditions, particularly at dawn or dusk when the sun is low in the sky.

The phenomenon is created when sunlight refracts and reflects off water droplets suspended in the air. The effect can produce faint, shimmering bands of light, often with a greenish or yellowish hue, that can appear in the sky. These light displays are generally less vibrant and dynamic than the aurora borealis and lack the characteristic dancing and swirling movements. The intensity and visibility of Kosteusrevontulet are highly dependent on the density of the fog or mist and the angle of the sunlight.

While visually similar to a dim aurora from a distance, Kosteusrevontulet is a purely atmospheric optical effect caused by light scattering within water vapor. It does not involve any geomagnetic activity or solar wind. The term is primarily used in informal contexts within Finland to describe these fleeting and localized light phenomena observed in moist atmospheric conditions.