A quote from Catholic Saints Information, “The Halo is symbolic of divinity and supreme power”. Divinity means of, or pertaining to god. The Holy Spirit is god, the third person of the Holy Trinity.
Notice how the supernatural orb looks exactly like the Halo:
I believe that the Halo can be seen in scripture as the Spirit of God alighting upon Jesus.
Mathew 3:16 When He had been baptized, Jesus came up immediately from the water, and behold; the heavens were opened to Him, and He saw the Spirit of God descending like a dove and alighting upon Him.
The Spirit of God alighting upon Jesus most likely appeared as a Halo.
In my opinion, the Halo can be nothing other than the Spirit of God.