日晕是一种奇特的光学自然现象，其表现为在太阳或月亮附近出现的光环。通常，这些晕预示着下雨，因为形成晕的冰晶被认为是雨云的前锋。本期视频会讲解晕的定义及形成原理，并且解释什么是日柱。

A solar halo is a strange optical natural phenomenon that appears as a halo around the sun or moon.Usually, these halos indicate rain, because the ice crystals that form them are thought to be at the front of the rain clouds.This video will explain the definition and formation of halo, and explain what the solar column is.