At about 7:00 a.m. on May 22, a rare celestial phenomenon appeared over the Chang'an District of Xi'an, Shaanxi Province, and the sun halo, the illusion of the sun, and the zenith arc were in the air at the same time, as if an angel had descended, which was amazing, and this phenomenon was also called "ice halo combination".
The solar halo, also known as the rainbow, is an atmospheric optical phenomenon formed by the refraction or reflection of ice crystals when sunlight passes through the cirrostorian clouds. When light rays enter the ice crystals in the cirratus cloud, they are refracted twice and dispersed into various colors of light in different directions.
The phantom sun is an optical phenomenon of the atmosphere. Inside the translucent thin clouds that appear in the sky, there are many hexagonal columnar ice crystals floating in the air, and occasionally they are neatly arranged vertically in the air. When sunlight hits this hexagonal icicle, a very regular refraction occurs.
The circumferential zenith arc, or Bravey arc, is an optical phenomenon that looks like a rainbow; however, it is formed by the refraction of sunlight from the horizon through ice crystals (usually located within cirrus clouds), rather than raindrops.