This is a recently-declassified US government photo of a hydrogen bomb detonating in space. The test, called Starfish Prime, set off the nuke 250 miles above the Earth's surface. NPR explains that the US did so see if the Van Allen radiation belts around the Earth had military uses:
The plan was to send rockets hundreds of miles up, higher than the Earth's atmosphere, and then detonate nuclear weapons to see: a) If a bomb's radiation would make it harder to see what was up there (like incoming Russian missiles!); b) If an explosion would do any damage to objects nearby; c) If the Van Allen belts would move a blast down the bands to an earthly target (Moscow! for example); and — most peculiar — d) if a man-made explosion might "alter" the natural shape of the belts.
Video at the link.
http://www.npr.org/templates/story/story.php?storyId=128170775 via DVICE
Given NPR's editorial leanings, it would be highly unusual for them *not* to point an accusing finger at a US nuclear testing program.
I don't know why Starfish Prime is being singled out as exceptional. The Krulwich piece on NPR is very interesting but it does leave the impression that Starfish Prime was unusual. Unfortunately, it wasn't. Check the Wikipedia entry on High-Altitude Nuclear Explosion.