A ring ground is typically constructed from a fairly large wire that is buried at least a few feet underground.
In the U.S., the National Electrical Code specifies that ring grounds must be constructed from #2 or thicker wire, must be buried at least 2 1/2 feet underground, and must have at least 20 feet of exposed copper to ensure good electrical contact with the earth.
The ground reference for all equipment inside the area being protected is separate from the halo.
A typical halo ground is constructed of #2 insulated copper wire and is installed six inches below the ceiling, and entirely encircles the area that it is protecting.
This is known as electromagnetic induction, and is the underlying principle used in the construction of electrical generators.