Sky Circle

There was a circle in the sky this afternoon. These were taken near the Oceanside CA pier.

It's the second time that I have seen something like it in this area. I also spotted a sky circle in the background of a news broadcast from Afghanistan. My speculation is that is a vapor trail from a military aircraft doing some type of maneuver in the sky.

I tried to run it down on the Internet. There are similar photos to be found but it quickly degenerates into a huge conspiracy theory about vapors being released into the atmosphere by some black government program. I am just at my limit on conspiracies and am unable to follow another one.

If you follow the trail it goes up over the sun.

If anyone has a clue as to why we see these in our sky let me know.