This time, a bunch of underwater mines exploded and the sun was the only suspect

Explosives go off without warning are bad news for … well, for Everybody. Imagine the alarm of the US military when, on August 4, 1972, she witnessed about twenty spontaneous explosions in the waters of Hon La in North Vietnam. The US operation Pocket Money had dropped submarine mines several weeks ago to deter commercial vessels from venturing into North Vietnam's ports. But the mines were supposed to explode only when the ships were nearby and the Americans watching the water above the water only saw light blue when the bombs exploded.

At first, the explosions were inexplicable. What could have triggered the mines? Large marine animals? Malfunctions of the equipment? Did the North Vietnamese use a secret strategy to blow up mines remotely?

More than four and a half decades later, we now know that the sun is the culprit. According to the findings recently published in the journal Space Weathera powerful solar storm probably triggered the magnetic sensors of the mines and blew them up.

"It was a storm of magnificent proportions," says Delores Knipp, a researcher in space meteorology at the University of Colorado, Boulder and lead author of the new paper. "It was a great story at the time and it continues." The storm occurred between Apollo Missions 16 and 17, but it is generally accepted that the radiation dose would have made astronauts unable (or even outright killed) to travel to and from the moon. In addition, other studies on the solar storm have revealed that the resulting geomagnetic current has created many power fluctuations in North America. "It's a storm that has had different effects in different communities."

That day, in 1972, for 30 seconds, US troops flying near northern Vietnam witnessed 20 to 25 explosions in the water and 25 to 30 additional mud spots. These mines use sensors to detect changes in the density of the surrounding magnetic field, which would normally be caused by passing a ship over the surface.

But something has clearly gone wrong. A few days after the event, representatives of the US Army were already wondering if the solar activity could have precipitated the detonations. At the time, scientists already knew that the sun was capable of changing magnetic fields, but they did not know if the solar activity reaching Earth was powerful enough to trap the mine sensors. Eventually, investigators working with the military and NOAA would quietly conclude that solar activity was probably to blame, but the case was not completely resolved.

With a deeper knowledge of solar activity, Knipp and his team plunged into documents now declassified and discovered that the 1972 event was an exceptionally strong solar storm and that several factors increased the effects when it hit the Earth.

Several hours before the bombs were fired, the sun started to explode and caused what is called a coronal mass ejection – a large, high-energy plasma vomit and radiation particles carrying electromagnetic pulses. It usually takes a day or two for these impulses to reach the Earth, but in this case, the previous two-day explosions were essentially crossing the interstellar medium, thus clearing the obstacles and opening up a pathway for the 4 ejection. August. The impulses finally hit the Earth in less than 15 hours and shook our magnetic coating with unusual force.

In fact, according to Knipp's research, the August 1972 storm was comparable to the Carrington event of 1859, one of the most powerful solar storms ever recorded. "It's our storm poster," says Knipp. "If such a serious storm were to happen again, we would really have a lot of problems." Our current world is extremely attached to communications instruments, power grids and technology, which can easily be destroyed by a particularly intense solar activity.

Which begs the question: how often do storms like these occur? The random operation of underwater mines is already a scary possibility to endure, but a loss of $ 40 billion a day for the US economy is simply unthinkable.

There is no direct answer to this question. After all, the whole field of space weather is a step forward in achieving that goal. For example, the advances of the last decade have illustrated how massive coronal mass ejections can occur in series rather than isolated events, allowing the team to determine why solar activity can be quite powerful. to trigger about twenty underwater mines.

But Knipp says that a general estimate, based on current knowledge, is that these types of solar storms hit the Earth about every 70 years – "often enough that it's necessary to think about types of technologies." likely to be damaged in these types of environment ". . "The question is not really if a storm powerful enough to destroy the power grid and destroy our technological equipment will hit us, but when that will happen and we will be ready in time to prepare and protect our infrastructure.