sädeympyräkoordinaatteja

Sädeympyräkoor is a Finnish term that translates to "radial halo" or "halo of radiation" in English. It refers to a specific type of optical phenomenon that occurs in the atmosphere, characterized by a circular halo of light surrounding a celestial body, most commonly the sun or moon.

This phenomenon is caused by the refraction and reflection of light through ice crystals suspended in the atmosphere. These ice crystals are typically hexagonal in shape and are found in high-altitude clouds such as cirrus or cirrostratus clouds. The specific shape and orientation of these crystals, along with the angle of the sunlight or moonlight, determine the size and appearance of the halo.

Sädeympyräkoor is a type of halo, and while the term itself is Finnish, the scientific principles behind it are universal. Other related halo phenomena include sun dogs (parhelia) and circumzenithal arcs, which are also formed by ice crystals. The appearance of a sädeympyräkoor can vary depending on the atmospheric conditions, including the size and density of the ice crystals and the position of the sun or moon. It is a purely optical illusion and does not indicate any change in weather or astronomical event beyond the presence of the necessary atmospheric conditions.