In Scientific Circles, they are known as “22-degree halos”. Because for an observer in a location the ring has a radius of approximately 22 degrees around the sun or moon.
And yet halos are a sign of high, thin cirrus clouds drifting 20,000 feet or more above our heads. These clouds contain millions of tiny ice crystals.
The halos you see are caused by both refraction, or splitting of light, and also by reflection, or glints of light from these ice crystals which are in hexagonal shape. Like rainbows, halos around the sun – or moon – are personal. That’s a person in Delhi may see rainbow or halo at 4pm but a person in Hyderabad may not because atmospheric conditions in a location are crucial to see halo/Rainbow