20 avril 2016

Super éruption solaire

Si une super éruption solaire (superflare) nous frappait de plein fouet, les effets seraient désastreux:

The paper explores the question of whether this is also something that can happen with our own sun.

The answer: not likely. Almost all the super flares the researchers looked at came from stars with much stronger magnetic fields than our own sun. A small but significant portion (about 10 percent), however, had magnetic fields of about our own sun’s size, meaning that the field is at least theoretically strong enough to generate a superflare.

So what would it look like in the unlikely event that we did get one?

During the superflare, the Sun would light up and become a few times brighter for the half an hour the flare would last. The superflare would likely also be associated with a lot UV and X-ray emission, but our ozone layer would shield us for most of this.

After a day or so the Earth would be hit by the plasma from the superflare. First the plasma would destroy all satellites around the Earth, shotting down GPS and communication system. Then particles from the plasma would get accelerated in the Earth’s magnetic field and cause world wide auroras, as it was seen after the 1859 solar storm (which was significant smaller than a superflare). The plasma would also affect the Earth’s magnetic field so much that it would start to induce electric currents in our electric infrastructure. This would likely led to power outage world wide, as in happened in Quebec during the 1989 solar storm. The Earth atmosphere would also be effected, so radar and radio system would be down, as in happened in Arlanda airport in Stockholm last year.

But the worst thing would be our ozone layer. Some simulations predict that the 1859 solar storm (the Carrington event) was associated with a 5% reduction of the ozone layer. Though these simulations have been criticised, it is still safe to assume that a superflare would cause a much larger reduction of the ozone layer… 5-10-50%. Our ozone layer protect us from 99% of the UV radiation from the Sun, so skin cancer could wipe out a significant fraction of the population and it is not clear what the increased UV radiation would do to animals and plants. The ozone layer would likely take more than 5 years to rebuild, and after that things should be back to normal.

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