During the Vietnam War, the United States strategically placed mines in North Vietnamese waters area that were set to detonate when a ship was in close proximity. In August 1972, a large number of these magnetic mines simultaneously started exploding. Upon investigation, the US found out that the cause of these explosions, which were estimated to be as many as 4,000, were not enemy ships. As it turned out, the culprit was located some 93 million miles away: the sun.

Solar Flares of 1972

In August 1972, a powerful historical series of solar storms with an extreme solar flare, solar particle events, and geomagnetic storm components hit the Earth. As defined by NASA,

Solar flares are powerful bursts of energy. Flares and solar eruptions can impact radio communications, electric power grids, navigation signals, and pose risks to spacecraft and astronauts.

That month, the sun unleashed a series of extremely powerful flares after increased solar activities. The burst of energy from these solar flares can be followed by coronal mass ejection (CME). A CME is like a cloud of radioactive particles from the sun expelled into the cold expanse of space at extremely high speeds. So high that normal CME can reach the earth in just one or two days, even when the sun is almost 93 million miles away.

The “seahorse flare” two-ribbon solar flare erupting from a very active sunspot region on 7 August 1972 and was recorded at the Big Bear Solar Observatory. (NASA, Public domain, via Wikimedia Commons)

While that was already an extreme speed, on August 4, 1972, flares sent a magnetized radioactive cloud toward the Earth, and it arrived in just 14.6 hours, or about 10 million kilometers per hour! It still remains the fastest CME travel time ever recorded that’s unbeatable until today.

Expectedly, such speed ticked all the sensors and monitoring devices all over the earth as they were doused with charged particles, sending their displays off the scales. The ejection also affected the planet’s magnetosphere resulting in bright auroras seen much further south and even reaching Spain.

The coronal mass ejection also affected the satellites and other spacecraft, with one satellite reportedly receiving wear that would usually take two years.

Triggering the Mines

Meanwhile, that same day, the US military pilots flying south of Haiphong harbor, North Vietnam, witnessed more than two dozen of sea mines suddenly explode in the water without anything at site triggering them. These underwater mines were designed to constantly monitor the magnetic field around them, which would change once a ship entered its proximity. The power of the 1972 solar storm distorted the Earth’s magnetic field enough that these mines were triggered around North Vietnam.

An American naval mine exploded in North Vietnam Haiphong Harbor during Operation End Sweep, photographed by the automatic mine locator camera aboard an American CH-53A Sea Stallion helicopter. It is believed to be the only mine explosion during End Sweep. The Mark 105 hydrofoil minesweeping sled the helicopter is towing is at the right. (United States Navy photograph, Public domain, via Wikimedia Commons)

The military already knew at that time that solar storms could mess with the system of the Earth, but it was not clear to them yet to what extent this could happen. Researchers at that time could not fully understand and explain the happenings caused by these CMEs yet.

New Light on the Event

It was not until research professor at the University of Colorado Boulder Delores Knipp explored the event in 2018 that the true scale of these sun flares of 1972 was realized.

According to their team’s reports published in the journal Space Weather,

The U.S. Navy attributed the dramatic event to magnetic perturbations of solar storms. In researching these events we determined that the widespread electric- and communication-grid disturbances that plagued North America and the disturbances in southeast Asia late on 4 August likely resulted from propagation of major eruptive activity from the Sun to the Earth.

Knipp and her team realized that the power of the storm at that time was way underestimated. She believes that the events were much closer in severity to the 1859 Carrington event, which was the largest geomagnetic storm recorded, although many failed to recognize it.

Knipp’s discovery of how intense these flares that triggered some 4,000 sea mines only showed us how truly vulnerable the Earth is, and everyone and everything in it, to the almost immeasurable powers of the Sun. And that 93 million miles is a distance that’s not far from its possible devastating touch.