Kehäräysilmiö

Kehäräysilmiö, also known as the "ring effect" or "halo phenomenon," refers to a visual optical illusion that can occur under specific atmospheric conditions. It is characterized by the appearance of a circular halo or ring of light surrounding a bright light source, most commonly the moon or the sun. The effect is typically observed when light interacts with ice crystals suspended in the atmosphere, such as those found in high-altitude cirrus clouds or during winter conditions.

The precise mechanism behind the kehäräysilmiö involves the refraction and diffraction of light. When light rays encounter the hexagonal facets of ice crystals, they can be bent or scattered. If the ice crystals are oriented in a particular way relative to the observer and the light source, the light can be concentrated into a circular pattern. The size and color of the halo depend on factors such as the size and shape of the ice crystals, the angle of observation, and the wavelength of light. While often associated with ice crystals, similar phenomena can sometimes be observed with water droplets in fog or mist, although the appearance may differ. The kehäräysilmiö is a naturally occurring atmospheric optics event and is not indicative of any unusual meteorological conditions beyond the presence of ice crystals at the appropriate altitude.