In the year 774 AD an enormously powerful explosion of matter and energy from space hit the earth.
Nothing like this had been felt on this planet for 10,000 years. A mix of high-energy light and hugely accelerated subatomic particles, when this wave hit Earth, it changed our atmospheric chemistry enough to be measured centuries later.
Our pre-electronic societies were totally unaffected by it. But if events like this happened today, the results would be bad.
It was first discovered through an analysis of tree rings, of all things. Scientists found that the level of carbon-14, an isotope of carbon, in rings from that year was much higher than normal. Several years later, when looking at air samples from ice cores, scientists noticed increased levels of beryllium-10 and chlorine-36 as well.
The common factor in all of these elements is that they form when extremely high-energy subatomic particles hit the Earth’s air and earth. They strike and change the atomic nuclei, creating these isotopes. The only way to get particles with such energies is from space, where powerful magnetic fields in exploding stars, for example, can accelerate the particles to such high speeds. We call these isotopes cosmogenic, made from space.
What had the space storm in AD 774? Can cause? The obvious candidate for such a thing is a very powerful solar flare, an explosion on the sun that occurs when intense magnetic field lines tangles and short circuits, releasing massive explosions of energy and particles. But the 774 event was so powerful that scientists were initially skeptical of an eruption. However, when any other type of astronomical phenomenon was ruled out, all that remained was an eruption.
A team of scientists went through the records to look at other such events in hopes of categorizing this eruption in comparison to other known eruptions. What they found is that this event was far more powerful than even some relatively scary modern flares.
For example, in 1989, the sun erupted in a powerful series of flares and a massive coronal mass ejection (or CME), ejecting billions of tons of hydrogen plasma at high speed. With its own magnetic field, this attack from space again struck the Earth’s magnetic field, affecting it so profoundly that electrical currents were generated beneath the Earth’s surface. Called geomagnetically induced currents, these extra electric power transformers in Quebec blew out and caused a power outage that lasted for hours.
February 1956 was the most powerful solar storm in modern times, which was easily twice as strong as in 1989. Our power grid was not used as extensively then, so it did not cause the same kind of damage as the 1989 event, but it still was a huge event.
Using different methods to characterize the 1956 storm, including measurements in visible light, radio waves, changes in the Earth’s ionosphere (a high-lying layer of ionized air that, when rapidly changing, can affect ground-based magnetometers that measure magnetic field strength ), and more, they found that the event in AD 774 was a dizzying event 30 to 70 times stronger. This means it probably was 100 times stronger than that of 1989.
It is not clear how long the torch lasted; the strongest grow and decay within hours. But the total energy released in this torch was about the same as what the entire sun radiates in one second: 2 x 1026 Joules, or the equivalent of about 100 billion one-megaton bombs going off.
That’s a lot of energy. Enough to power our entire planet (given our current energy consumption) 300,000 years.
Yegads.
Such a torch becomes one superflare, and until now it was not thought that the sun could produce them (other stars that are more magnetically active make them quite often). The scientists think the 774 torch may have been a special circumstance, in which a powerful torch happened near a gas streamer called a filament that strikes it and accelerates the protons in it to such high energies.
That is actually a relief! I prefer it hard for the sun to do this.
Such an event taking place today would be catastrophic. It could knock out countless satellites – the particles and high-energy radiation can even short circuit hardened electronics – and cause widespread blackouts. Solving those problems can take a long time because the larger transformers used by power grids cannot be mass-produced. Some scientists calculated that passengers on international plane flights could receive a lifelong dose of radiation within hours of such an event.
The effects on Earth can be difficult to determine; in part it depends on whether the torch and the magnetic polarity of CME (the north-south part of the magnetic field) are able to couple with the magnetic polarity of the earth. If so, we get the blackouts and other damage. But some effects occur in both ways.
I will note that we haven’t seen a powerful event since 774, although many were quite strong. The sun erupted in 2012 in a coronal mass ejection that, had it hit Earth, would have been worse than the 1989 event. Fortunately, it was sent in a different direction.
But it is clear that the sun can have some pretty big tantrums, and we have to take this seriously. Certainly solar astronomers, and as the sun rises in the latest magnetic cycle, they look at our star with everything they have. We don’t know how strong this cycle will be; one prediction is that it won’t be a problem, but another says it will be very bad.
We will see. Clearly, there is much more we need to learn about the sun. It is no exaggeration to say that our modern life depends on it.