During the Cold War, the U.S. and Soviet Union detonated nuclear weapons in the upper atmosphere to study the dynamics of a nuclear explosion. Yes, we detonated nuclear bombs in our upper atmosphere. Can you imagine if a country did that today? Regardless, much was learned from the tests.
The more popular and well known test was Starfish Prime. July 9th marked the 50th anniversary of Starfish Prime which involved the detonation of a 1.4 megaton nuclear bomb about 900 miles south of Hawaii.
The feathery filament is from the bomb debris, while the red glow may be due to glowing oxygen atoms; this tends to be from atoms higher than 100 km, so the glow is probably due to the heavy ions impacting our air.
The blast also produced an EMP which was also caused by the rapid ejection of electrons. When electrons are accelerated as fiercely as they are during a nuclear blast, they create a very powerful magnetic field.
When the bomb detonated, those electrons underwent incredible acceleration. When that happens they create a brief but extremely powerful magnetic field. This is called an electromagnetic pulse, or EMP. The strength of the pulse was so huge that it affected the flow of electricity on the Earth hundreds of kilometers away! In Hawaii it blew out hundreds of streetlights, and caused widespread telephone outages. Other effects included electrical surges on airplanes and radio blackouts.