The light of the sun.
Sunbeam (crepuscular rays) is where light rays stream through gaps in clouds or between other objects. These are columns of sunlit air separated by darker cloud-shadowed regions. (See Danbooru post #438675)
Sunburst is for designs or figures of burst of sunlight, but may not necessarily be the actual sun (See Danbooru post #645306)
For tagging purposes, keep in mind that a particular image may satisfy one or more of the specific terms mentioned above.