Phew! You may not have known it, but Earth barely missed the "perfect solar storm" that could have smashed into our magnetic field and wreaked havoc with our satellite systems, electronics and power systems, potentially causing trillions of dollars in damage, according to data from NASA's STEREO-A spacecraft.
On July 22, 2012, STEREO-A spotted what looked like an enormous solar eruption sending out a coronal mass ejection at blazing top speeds of roughly 1,800 miles per second – the fastest ever recorded by the spacecraft. By the time it actually passed STEREO-A a mere 17 hours later, the magnetic cloud was still traveling at 750 miles per second. That's about three times faster than your typical coronal mass ejection, which runs into Earth at an average speed of about 280 miles per second, according to a study in the journal Nature Communications.
[Updated at 6:28 a.m., March 20: It's a good thing this incredible blast wasn't pointed at us, scientists said.
"This record solar wind speed and magnetic field would have generated the most severe geomagnetic storm since the beginning of the space era, if the event had hit the Earth," the study authors wrote."]
This above-average event was the result of a perfect storm in outer space, according to an international team of researchers, led by Ying Liu of China's National Space Science Center. There was actually not one, but two coronal mass ejections that erupted from the same region of the sun within 10 to 15 minutes of one another that tangled close to the sun and then barreled into space. And while most storms tend to slow down pretty quickly, this one didn't, because an earlier coronal mass ejection four days before had blazed a path through space and cleared out any obstacles that would have slowed it down.
If the solar onslaught had occurred just nine days earlier, it would have rivaled the 1859 Carrington event, a solar storm that zapped the telegraph system, delivering shocks to telegraph operators, and triggering aurorae -- a typically polar light show in the sky -- as close to the equator as Hawaii and the Caribbean. Today, such a storm would have caused far more damage in our now highly wired world, utterly dependent on electronics. (As further comparison, a much weaker geomagnetic storm in 1989 caused Quebec's power grid to fail.)
There are multiple dangers to a solar storm. A massive eruption of material from the sun, known as a coronal mass ejection, can release roughly a billion hydrogen bombs' worth of energy. This sends a magnetic cloud of material at extremely high speeds barreling into space. And if this cloud slams into Earth's magnetic field, the resulting mashup can cause a geomagnetic storm that can disrupt satellites and power grids. Such solar eruptions can also hurl out a super-fast blast of energetic protons traveling near the speed of light that can disrupt radio communications, including those made by airline pilots.
At the time, STEREO-A was sitting about 89 million miles away from the Sun – roughly the same distance as the Earth, which is about 93 million miles away. Luckily, the storm was pointed away from Earth, in the direction of STEREO-A.
A recent study indicated that a storm like the 1859 Carrington event would have caused up to $2.6 trillion in damage here on Earth. This near-miss storm could potentially have caused damage on a similar order.
And the fact that it did happen during what was a historically weak solar cycle hints that such dangerous storms might be more common than we think – and may require more study in order to accurately predict and prepare for them.
"Observations of such a solar superstorm during a very weak solar cycle indicate that extreme events are not as infrequent as we imagine," the authors wrote.