Does Earth need a solar shield?
We talk frequently of the asteroid threat, but perhaps we should do more to protect Earth from solar storms
The Sun nurtures all life on Earth, but its fractious and sometimes violent nature also threatens our industrialised, technological civilisation. Consider the large coronal mass ejection (CME) that struck Earth in 1859, known as the Carrington Event after the British astronomer who observed the associated flare on the Sun’s surface. When that CME hit Earth’s magnetosphere it triggered auroral displays as close to the equator as the Caribbean, and induced a huge geomagnetic storm that caused sparks to fly from telegraph wires.
That was in an essentially pre-electric world; the damage inflicted on the world today by a similar event would be catastrophic. In particular, an extreme solar outburst could knock out satellite communications and global positioning systems (which are used nowadays not just for navigating your way around, but also for the timing signal used in many financial transactions) as well as inflict severe damage to electrical power grids, which could take years to repair.
It’s been estimated that were the Carrington Event to hit the world now, it could cause a total global economic loss of up to $10 trillion. So what might we realistically be able to do to protect Earth from the impact of a CME?
Manasvi Lingam and Abraham Loeb at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, have explored the plausibility of humanity building an electromagnetic deflector in space to shield the Earth. Their paper is intended more to highlight the very real hazard posed by CMEs, which the authors say has not received as much attention as asteroid impacts or terrestrial natural disasters, rather than to propose a fully-planned engineering solution. But Lingham and Loeb do present some first-order physics calculations to work out what might be required.
If an electromagnet were placed at the L1 Lagrange point between the Sun and Earth, where the gravitational and centripetal forces are balanced, it would not need to be very powerful to deflect a CME around the planet: only around 0.01 per cent of Earth’s magnetic field strength would be enough.
Even so, this would demand a huge amount of power whilst the shield was switched on (although
“Were the Carrington Event to hit the world today, it could cause a total global economic loss of up to $10 trillion”
this electricity could be provided by solar panels) and a colossal electromagnet coil structure to be assembled in space. The authors calculate that if the deflector coil were constructed with copper wire it would need about 100,000 tonnes of the metal (200 times more than the International Space Station) to be launched. They also estimate the launch cost to be around $100 billion, comparable to the total price tag of the ISS. These figures could be reduced if a superconducting coil were used instead, or perhaps the necessary materials were mined from an asteroid rather than launched from Earth. But either way, this would be certainly a large commitment.
Building a giant space deflector shield might sound like something straight out of sci-fi, but the authors stress that it can be built with current technology, and at a fraction of the cost of the economic losses that could be inflicted if we did nothing. This might well represent a very sensible insurance policy for us all.