Pollen corona

Pollen coronas are formed by the diffraction of light on the pollen of wind-pollinated plants. The pollen grains of the same tree species generally have a similar size and are therefore ideal for forming diffraction patterns. Since pollen grains are comparatively large, they produce very small coronas. To see them around the dazzling sun, it is essential to wear dark sunglasses to protect the eyes, and the sun should be covered by tree tops, roofs, or similar! Unlike water droplets, most pollen grains are not spherical. Many have air sacs to aid wind dispersal. Depending on the type of pollen and their orientation in the air, the coronas have an oval to diamond-shaped appearance with distinct "light nodes" when the sun is low in the sky. As the sun rises higher, all coronas become increasingly round due to the changing angle of view. A precondition for visibility is a very high pollen concentration in the air. It is greatest after an extended dry period with light to moderate winds. Many weather services point out high pollen counts in their forecasts, and there are now many websites with current pollen flight information, such as on the page of the DWD.

The pine corona is probably the most frequently observed type of corona. One reason is certainly that there are countless pine forests in the central German area, and the pollen can be carried by the wind over hundreds of kilometers. Even in areas with few pines, pine coronas can still occur. The best time for observation is from the end of April to the beginning of June during longer dry periods with light winds. Pine pollen have a slightly bent shape with two airbags on the sides. Their coronas have distinct light knots on the sides as well as above and below when the sun is low.