Solar storms are not even in my top five list of threats to humankind (nuclear war, asteroid strikes, super-volcano eruptions like Yellowstone, a supernova within 30-50 light years, and intergalactic pirates), but they are still worth talking about. Especially because there may be an easy way to protect ourselves from the worst effects of solar storms.
Nobody knew anything about such storms until two centuries ago, when a big one scrambled all of the world's long-distance communications. But the technology was new (electric telegraphs and the batteries that powered them), and apart from that, electricity had few practical uses. The solar storm was therefore just a transitory nuisance, not a global disaster.
It became known as the Carrington Event, named after Richard Carrington, the British astronomer who witnessed the solar storm, a "coronal mass ejection" from the Sun on Sept 1, 1859. Thinking laterally, he linked it to the worldwide electrical outage that happened only a few hours later. It stirred a lot of interest in the scientific community, but not much in the rest of the world because power grids, light bulbs and electric motors had not yet been developed. Now, however, electricity is indispensable in almost every industrial, commercial and domestic activity worldwide, and it turns out that these Carrington-like events happen quite often.
They vary in size, and there hasn't been one as big as the 1859 monster since then. However, smaller "mass ejections" are blasted out of the Sun two or three times a day during the peak phase of the eleven-year sunspot cycle, and most of them are travelling in or close to the ecliptic (the plane of the Earth's orbit).
The biggest one was in 775, when we know (from carbon-4 isotopes trapped in the rings of ancient trees) that a solar storm ten to one hundred times more powerful than the 1859 incident hit our planet. No harm done, because no electricity under human control. Now it would be a catastrophe, even if it were only the same strength as Carrington's event.
When massive solar storms smash into the Earth's magnetic field, they deliver energy and charged particles that scramble satellite electronics. They may even bring satellites down by heating and expanding the stratosphere upwards into their orbits.
On the ground, huge electrical currents surge through power grids and transformers, often not just knocking them offline (fixed within a day or two) but burning them out (one or two years to replace them).
No internet, no GPS, no coordination in just-in-time delivery systems. An eight-billion-strong world trying to cope largely with surviving pre-1950s technologies, and probably on the brink of famine while they struggle to rebuild a 2020s world. Not a terminal disaster, but you'd pay a lot to avoid all that. What kind of protection could you buy?
Here come the scientists with an idea called StormWall, and they're not even asking for money. The idea, published this month in Space Weather, is that human beings can reduce the impact of incoming geomagnetic (solar) storms on Earth by more than half by releasing huge canisters of a neutral gas (lithium, barium or sodium gases) or even plain salt water in orbit.
Six heavy-lift rockets (Musk's Starship or China's Long March 9) would lift the canisters into a geosynchronous orbit, 36,000 km/23,000 miles from Earth but still within its magnetic field. There they would wait, perhaps for many years, until monitor satellites spot a solar storm headed for Earth that is big enough to kill human electrical and electronic devices. Then they dump their load of around 400 tonnes of neutral gases into space, and sunlight will rapidly ionise it into a plasma that essentially absorbs much of the incoming energy (more than 50%). If everybody on Earth powers down at the same time to protect their devices, the damage could be relatively slight. This is a brand new idea, so it will take a lot of work before everybody is happy, but the plasma does no harm and will disperse rapidly into space. All the technology involved is available now or in the very near future. As co-author Daniel Welling of the University of Michigan said: "It's as if you could install an airbag in the magnetosphere."
