Youtube video of the Iridium-6/GRACE-FO NASA Launch (Falcon 9 SES-12).
Edit 31 May: Too bad they have changed the content of the video (and still call it 'live'), so that you can no longer see the entire launch phase. You can still see that in this video showing the entire launch.
There's one ring visible at the top of the rocket after 1:30 minutes into the launch and it seems to emit light:
Shortly after 1:50 into the flight, you see 3 more 'rings' developing:
This is after going supersonic (1:11) and maximum dynamic pressure (1:24).
They must be some sort of bow waves/shock waves. But:
- Why is there only one, later 4?
- Do they (especially the top one) really emit light?