Why is the rainbow around the sun, what does it mean, what is this phenomenon?

This is called the sun halo. Halo (halo, nimbus, icebow, gloriole) is an optical phenomenon formed by the refraction or reflection of sunlight or moonlight by ice crystals suspended in the atmosphere. The halo is usually ring-shaped or arc-shaped, and has seven colors: red, orange, yellow, green, blue, indigo, and violet.

The reflection of ice crystals from the sun to the human eye is called "solar halo", while the reflection of ice crystals from the moon to the human eye is called "lunar halo". Ice crystals in the atmosphere are usually brought by cirrus clouds, and when sunlight hits the ice crystals, they are reflected off the human eye, creating rings or arc-shaped coils, usually red on the inner and violet on the outside. Halo can be divided into "small halo" and "large halo", "small halo" is 22 degrees of halo, and "large halo" is 46 degrees of halo.

The small halo is a light red inner ring with a light red inner circle with a radius of 22 degrees and an occasional purple or white ring with a luminous body as the center and an outer circle, and the sky inside the halo is significantly darker than the outside of the halo. The large halo is a halo with an angular radius of 46 degrees, which is very rare and generally darker than the small halo. There is a proverb in our country called:

The moon is faint and the wind is faint, and the sun is rainy. This means that after the appearance of the lunar halo, there will be strong winds, and after the appearance of the solar halo, there will be heavy rain...

After a rainy day, the water vapor in the air is more abundant, and the sunlight shines on these water vapors, forming a dispersion, which causes a seven-color rainbow, and its condition is that there must be sunlight, so the rainbow always surrounds the sun.

I think what you're seeing should be a solar halo.

And the moon halo. I also often see that there are other days and moons, and I don't know what kind of phenomenon you are talking about, so I will find a text to explain it to you.

Optical meteorological principle of halo.

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Halo is an optical phenomenon in nature. It is due to the refraction of ice crystals when the light rays of the sun or moon pass through high, thin white clouds (cirrus, cirrostratus or cirrocumulus), which are arranged in ultraviolet red. The circle of light that appears around the sun is called the solar halo, and the circle of light that appears around the moon is called the lunar halo.

When there is a halo, there is usually no wind and thin clouds (cirrus, cirrostratus, or cirrocumulus) float in the sky. Cirrus, Cirrostratus, and Cirrocumulus are mostly composed of ice crystals. In order to know that light is refracted by ice crystals and causes halos, and to see halos in the sky, it is necessary to understand what kind of clouds cirrus, cirrostratus and cirrocumulus clouds are and what kind of weather conditions they are.

Cirrus, which is a number of very thin, white, feathery clouds, often appearing in sheets or narrow bands, with a very high base. Cirrus clouds often signal the arrival of cold air or upper-air depression, with the presence of precipitation. There is a proverb that says:

Hook clouds in the sky, rain on the ground", refers to a kind of cirrus cloud in the clouds. Cirrocumulus, which is often white and thin, like fluffy cotton and like tiny fish scales, is sometimes confused with Altostratus, but isolated clouds are generally smaller than Altostratus. There is a proverb that says:

Fish scale days, no rain is crazy", cirrocumulus clouds are often a precursor to wind and rain. Cirrostratus, which is flakes or layers, varies greatly in thickness, sometimes very thin, you have to be very careful to see it, and sometimes thick enough to shade the sun. Cirrostratus clouds often indicate changes in weather systems.

There is a proverb that says: "The sun is halo and the rain is three, and the moon is halo and the wind is at noon", but not necessarily every halo brings wind and rain.

So, how is halo formed? Why is the inner ultraviolet red and the outer red?

The ice crystals in Cirrus, Cirrostratus and Cirrocumulus are mostly hexagonal prisms, and when sunlight enters the atmosphere, the ice crystals act as prisms, and after two refractions, the sunlight is dispersed into colored light in different directions. Because sunlight is composed of red, orange, yellow, green, blue, indigo, and violet, due to the different refractive indices of different colors of light (among them, the wavelength of red light is the longest, the refractive index is the smallest, and the wavelength of violet light is the shortest, the refractive index is the largest, and the phenomenon of different refraction directions produced by different colors of light is called dispersion), after being refracted by ice crystals, the deflection angle is also different, and the minimum deflection angle is about 22

The rainbow that appears around the sun is often referred to as a halo and is an optical phenomenon formed by the refraction, reflection and scattering of sunlight through water droplets or ice crystals in the pure air of the Great Luzhao.

When sunlight passes through water droplets or ice crystals in the atmosphere, refraction, reflection, and scattering occur, forming some special rays of light. Among them, refracted light refers to the light formed by sunlight after refraction by water droplets or ice crystals, reflected light refers to the light formed by sunlight after reflection by water droplets or ice crystals, and scattered light refers to the light formed by the scattering of gas molecules in the atmosphere. These rays undergo complex reflection, refraction, and scattering to form a rainbow-colored aura.

Specifically, the halo usually appears as one or more iridescent rings around the sun, the most common of which is a iridescent ring, which is known as the "22-degree halo." It is formed due to sunlight being refracted by, reflected, and scattered by ice crystals in the atmosphere. Other halos, such as 46-degree rings and 120-degree rings, are also formed by the refraction, reflection and scattering of sunlight through chain-wide ice crystals in the atmosphere.

The appearance of these rings depends on factors such as the type, density, shape, and size of the ice crystals in the atmosphere.

It is a solar halo, indicating that it may rain late at night.

This is caused by the fact that sunlight hits the air and is close to a spherical shape, causing dispersion and reflection.

When sunlight hits a water droplet, it is incident at different angles at the same time, and it is reflected at different angles within the water droplet. To cause this reflection, sunlight enters the water droplet, first refracts once, then reflects on the back of the droplet, and finally refracts again when it leaves the droplet, for a total of two refractions after one reflection.

Because water has a dispersive effect on light, the refractive index of light of different wavelengths is different, red light has a smaller refractive index than blue light, and blue light has a greater deflection angle than red light. The spectrum seen by the observer is reversed, with the red light at the top and the other colors at the bottom.