Halosäteitä

Halosäteitä is a Finnish term that translates to "halo rays" or "light rays" and refers to atmospheric optical phenomena that appear as rings, arcs, or pillars of light surrounding a light source, most commonly the sun or moon. These halos are created by the refraction and reflection of light by ice crystals suspended in the atmosphere. The specific shape and appearance of the halo depend on the size and orientation of the ice crystals, as well as the angle of the sun or moon.

The most common type of halo is a 22-degree halo, which forms a ring around the sun or moon with a radius of approximately 22 degrees. This is caused by hexagonal ice crystals that are oriented randomly. Other types of halos include circumzenithal arcs, which appear as vibrant, upside-down rainbows above the sun, and sun pillars, which are vertical shafts of light extending upwards from the sun. These phenomena are more commonly observed in cold regions where ice crystals are present in the air, but can occur anywhere under the right atmospheric conditions.

Halosäteitä have been observed and documented throughout history, often interpreted as omens or divine signs. In meteorology, they are indicators of high-altitude ice clouds, such as cirrus clouds, and can sometimes precede changes in weather. While visually striking, halosäteitä are harmless optical illusions and do not pose any physical danger. Their formation is a beautiful illustration of the interaction between light and atmospheric ice.