Parelium

Parelium is an atmospheric optical phenomenon mainly associated with reflection and refraction of sunlight by small ice crystals from Cirrus or Cirrostratus clouds. Often, two parelios can be observed (one on each side of the sun at 22 ° if the sun is on the horizon line) simultaneously.

The formation of the parelium is similar to the halo, but since the ice crystals have a different orientation, it is characterized only as two colored spots, like two parts of a halo, at a certain distance from the sun, one from each. side. The higher the sun is in the sky, the farther one parelium is from the other. Considering the condition of the sun on the horizon, the result is parellia at 22 degrees from the sun, and if there is a halo present they "touch" the halo.

The parelium usually shows a whitish "tail" pointing away from the sun. In fact, this glow is formed by the exit beams that have experienced greater deviations. It is the equivalent, at a 22 ° halo, of the whitish glow outside. Since the crystals have unique cloud orientations parallel to the surface, a larger number of crystals contribute to the formation of the parelium compared to the halo.

In the halo, many crystals are simply totally out of the required orientation. The chance that a crystal is properly oriented to form a parelium is greater, so this phenomenon is often brighter than the halo. The whitish tail may even be strong, varying in size in the sky.

In some cases the crystals have slight deviations in their orientations, all not being perfectly with the bases parallel to the surface. The parelium, in this case, will have a small vertical extension, resembling really a small piece of halo. There is a maximum sun height relative to the horizon at which a parelium can form, which depends on the relationship between the height and width of the crystals.