At the time they didn’t have the means to detect and track a CME (Coronal Mass Ejection), but the technology was impending, due in part to the events that were transpiring. This time instead of forecasting an aurora that might occur naturally, they were creating one. Specifically, DASA (Defense Atomic Support Agency) and the AEC (Atomic Energy Comission) were creating the aurora by means of a suborbital nuclear detonation.
The test was codenamed Starfish Prime, and was part of Operation Dominic, a series of tests designed to test the abilities of nuclear weapons in space.
The W49 thermonuclear warhead was launched on the nose of a Thor rocket. The warhead detonated 248.5 miles above Johnston Island—an altitude that is considered outer space. The yield of the blast was 1.5 Megatons, but there was no fireball. There is no air at that altitude to ignite. That is not to say, however, that there were no visual effects.
Quoting Cecil R. Coale, PhD , who observed the flash from Canton Island:
Then a brilliant white flash erased the darkness like a photoflash. Then the entire sky turned light green for about a second. In several more seconds, a deep red aurora, several moon diameters in size, formed where the blast had been. A white plasma jet came slowly out of the top of the red aurora (over Johnston Island) and painted a white stripe across the sky from north to south in about one minute. A deep red aurora appeared over Samoa at the south end of the white plasma jet. This visual display lasted for perhaps ten minutes before slowly fading. There was no sound at all.
As spectacular as the sight was, it was the invisible features of the blast that were the most impressive. Not only was the sky illuminated, but in Hawaii alone 300 street lights failed, TV and radios malfunctioned, burglar alarms went off, and several power lines fused. In low Earth orbit 3 satellites were immediately disabled, and some artificial radiation bands were created that eventually disabled 1/3 of the low orbit satellites in orbit.
Obviously the aurora effect was predicted, but as is expected in government jobs, most of the rest came as a surprise—including the fact that after the explosion they realized that they had no rockets or equipment to follow the bomb and study the aftereffects of the test.