Kind of self explanatory in the title, but yeah, I’ve been curious about this ever since I read about the Carrington Event and how it would effect us in modern times.
In: Planetary Science
Nobody is 100% certain. Also it would depend massively on which side of the planet is facing the sun when the flare reaches us. Luckiest possible scenario would be something like noon in Hawaii, but even then the effects would be widespread.
Best guess is something like the following. First, we would probably have a few hours warning before the main effects reach the planet. This would be enough time to scram power plants, disconnect major substations, etc. Electrical grids around the world would be shut down as rapidly as possible. Inevitably, the vast majority of smaller substations would remain connected, which would lead to some problems later.
Most telecommunications backbone is fiber at this point. There’s some legacy copper here and there which would cause some problems but, by and large, the fabric of the internet would be fine (albeit unpowered). It is, at this point, worth remembering the old chestnut about how the original DARPANet was designed to withstand a nuclear attack. A repeat of the Carrington Event would be much like a global nuclear airburst, so a lot of the same EMP-related principles apply.
Almost all satellites would suffer massive damage. We really don’t know how bad this would be, but “bad” is a very safe bet. Some satellites (particularly more recent military hardware) are hardened against this type of EM flux, but most are not. It’s a safe bet that GPS and its clones are knocked offline. Starlink is very unlikely to survive. Weather data, climate studies, etc. All of that would be bad. Oh also any astronauts on the ISS would immediately leverage the emergency escape craft to return to the surface, and we would have to go pick them up quickly before our ground infrastructure crashes.
Once the flare reaches the planet, the worst of the impacts would be on the power grid. Even with most potentials large disconnected and grounded, the massive amount of conductive wiring stringing around developed countries would act like an array of giant antennas, capturing the flux and magnifying its potential. Any transformers or other equipment not isolated from transit infrastructure would probably just explode, with the obvious consequences. The uncountably numerous small transformers which dot every neighborhood of every settled area of the developed world would *likely* see flux in-excess of their rated maxima, which means *they* probably mostly explode or at least are damaged beyond repair. Massive manufacturing backlogs would rapidly become the bottleneck for re-energizing major swathes of the grid, particularly in the mid-sized substations that are both hard to manufacture and replace, but also too numerous to have all been protected prior to the event. Take a look at some of the challenges Ukraine has faced in sourcing its grid-scale replacement components in large quantity after Russian attacks.
Cell networks would be a priority but, without grid power they would only last a few hours. True antennas and radio towers would probably do just fine, since they’re designed to withstand much more significant potentials during thunderstorms, and they wouldn’t be gathering quite as much current from a flare.
The only grid infrastructure to survive (apart from the aforementioned physically disconnected pieces scrammed prior to the event) would be that which is buried. There’s not a small amount of this, particularly in cities, but it’s still the vanishing minority of the whole. This likely means that, post-apocalypse, dense urban areas would be the first to see power restored. It would still probably take weeks to gently massage the grid back online. Parts of developed countries would likely remain without power for months, with the predictable consequences of lots of moaning and complaining. Cell networks would be restored very quickly, likely using generators.
Over years and decades, some of the destroyed near-space infrastructure would be restored, notably GPS. Given its technical and political problems, the ISS might simply be abandoned. The learnings from the flare would inform the design of future satellites and spacecraft, to say nothing of grid operating procedures.
Total economic price tag would be in the trillions, mostly in lost productivity, but it’s hard to say for sure. Imagine most wealthy countries engaging in significant economic stimulus to blunt the impact (think: what happened in 2020).
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