Cold War data reveals impact of nuclear tests on space weather
The Cold War may have been over for a quarter of a century, but its effects that reached far beyond just geopolitics are still being uncovered. One case in point is a NASA study that used recently declassified US government data to show how high-altitude nuclear tests altered the weather – not on Earth, but in space. According to the space agency, the explosions changed the planet's magnetic field and even produced artificial aurorae near the equator.
Mention the 1950s and it brings up images of huge American cars with fins, rock and roll singers, poodle skirts, and hula hoops. Unfortunately, it also recalls the darkest days of the Cold War when the Soviet Union and the Western powers were locked in a struggle for world domination that thankfully didn't move into open conflict.
The main reason for this so-far-and-no-further policy was the arms race between East and West to create ever more powerful nuclear weapons, which required hundreds of test explosions above ground, at sea, and in the air. Between 1958 and 1962, the Americans and Soviets even conducted high-altitude tests that reached to the edge of space.
The Partial Test Ban treaty of 1963 put paid to most of that as testing was restricted by an agreement between the superpowers to restrict explosions to below ground. However, the data from those tests already conducted still remains and, as some of it has become declassified, it's told a very interesting story to NASA scientists about the bomb and the weather.
During the heyday of above-ground testing, the bomb was blamed for many things, including altering the Earth's weather. That turned out to be false. Or maybe not, if you're talking about space weather rather than the terrestrial clouds and rain variety.
Space weather refers to the magnetic and radioactive environment beyond our atmosphere. The Sun is a gigantic fusion reactor belting out a continuous, invisible gale of subatomic particles punctuated by massive solar flares belching plasma into the vacuum and seasoned with cosmic rays from deep space.
In other parts of the Solar System, these solar winds and cosmic radiation have had a devastating effect as the winds rip away the atmospheres of smaller planets and moons, leaving them defenseless against radioactive bombardments. But the Earth is protected from this by its powerful magnetic field, which acts as a bubble that deflects or captures the charged particles coming from the Sun.
These trapped particles produce the twin Van Allen belts situated between 1,000 km (620 mi) and 60,000 km (37,300 mi) above the Earth. These belts protect us, but they are also a major hazard to space navigation due to their intense radiation. When the trapped ionized particles in the belts follow the magnetic lines of force to the North and South poles, they strike the atmosphere and create the famous aurorae.
Space weather is also not very stable. If there's a magnetic storm or a solar flare is large enough and pointed in our direction, satellites can be knocked out, radio communications cut off, compasses thrown out of true, power grids overloaded, and even electronics fried.
By comparing the energies generated by the atomic tests to those of natural space weather events, the NASA researchers were able to tell the difference between fission-generated particles and those from the Van Allen belts. This way, they were able to isolate and draw conclusions about the effects of nuclear explosions.
What NASA found was that a series of US nuclear detonations at altitudes from 16 to 250 mi (25 to 400 km) did more than produce a bright flash and loud explosion. The plasma generated by the fireball at temperatures of over 10 million degrees had very severe local effects, distorting the Earth's magnetic field and even creating miniature radiation belts that interfered with satellites.
According to NASA, the 1958 Teak test over Johnston Island in the Pacific created an artificial aurora over Western Samoa south of the Equator – just the place where one does not expect to find aurorae. The study team says that this unusual phenomenon could help scientists gain a better understanding of natural aurorae.
Also in 1958, the Argus test produced a geomagnetic storm from Sweden to Arizona as two high-speed waves traveled across the globe at up to 1,860 mph (2,993 km/h), creating artificial radiation belts that lasted only a few seconds.
One thing that NASA does not mention is that, while the nuclear effects were severe on a local level, the energies and effects involved were minuscule compared to that of emissions from the Sun interacting with the Earth. Compared to the latter, the largest nuclear test ever would be like comparing a bar tab to the US national debt. However, the study does promise to have practical applications.
"The tests were a human-generated and extreme example of some of the space weather effects frequently caused by the Sun," says Phil Erickson, assistant director at MIT's Haystack Observatory, Westford, Massachusetts, and co-author on the paper. "If we understand what happened in the somewhat controlled and extreme event that was caused by one of these man-made events, we can more easily understand the natural variation in the near-space environment."
The research was published in Space Science Reviews.
The video below illustrates the principles behind the study.