A great visual example of corona discharge from an ozone generator is available at the video below:
Corona discharge occurs when we place electrical current through a dielectric to diffuse that spark accross a greater area. This antique ozone generator shows the corona discharge between each of these quartz tubes that are energized.
This antique Vitozone ozone generator operates very differently than today’s ozone generators. However, this is an interesting example of what an ozone generator looks like and works like.