How Far South Could You See The Aurora With A Perfect Solar Storm?

How far south/north could the Auroras be seen if the atmospheric conditions were perfect and the earth was hit with the perfect solar storm and would there be other effects?
ESA astronaut Alexander Gerst took this image of an aurora as he circled Earth on the International Space Station. Aurora occur when electrons from the Sun hit Earth's atmosphere. Auroras occur frequently over both the North and South polar regions, but are often difficult to see from populated areas. Alexander is a member of the International Space Station Expedition 40/41 crew. He spent five and a half months living and working on the Station for his Blue Dot mission. Image Credit: ESA/NASA

ESA astronaut Alexander Gerst took this image of an aurora as he circled Earth on the International Space Station. Aurora occur when electrons from the Sun hit Earth's atmosphere. Auroras occur frequently over both the North and South polar regions, but are often difficult to see from populated areas. Alexander is a member of the International Space Station Expedition 40/41 crew. He spent five and a half months living and working on the Station for his Blue Dot mission. Image Credit: ESA/NASA

Originally posted at Forbes!

We have a pretty good template for this one, actually, because the Earth was hit with a very powerful solar storm in 1859. The solar flare that started it off was observed by Richard Carrington, who had a history of sunspot-watching, and his name got attached to it, and so we know it now as the Carrington Event.

1859 is an interesting time; our scientific understanding of the Sun and aurora was advanced enough to recognize basically what had happened, but we humans hadn’t become as reliant on sensitive electronics during our daily lives, so the electromagnetic disruption was not too severe. (A Carrington-scale event occurring today would cause much more severe disruption. You would notice. A lot. More on that later.) 1859 was also recent enough that we have a lot of records of what people saw that evening.

Even with a minor solar storm, if you’re far enough North or South (in other words, if you’re close enough to magnetic north and magnetic south on our planet), it’s not too hard to spot the aurora on a clear night.  It helps if there’s no moon, but with dark skies you can spot them without too much trouble. This is one reason some of the most spectacular recent images of the northern Lights tend to come from places near the arctic circle, like northern Scotland, Sweden, Norway, and Alaska. (You can also get excellent images from space, but that's cheating.) It’s harder to spot the Southern lights with the same ease, but that’s just because no one lives in Antarctica, and the next most habitable places are farther removed from the southern pole.

It is cold, dark, dry and isolated with very little oxygen to breathe in the air, but the unique location makes Concordia station in Antarctica an attractive place for scientists to conduct research. The aurora australis that adds colour to this picture is a well-deserved bonus for the crew of 13 who are spending the winter months cut off from friends and family. Image credit: ESA/IPEV/PNRA–B. Healey, CC BY-SA 3.0 IGO

It is cold, dark, dry and isolated with very little oxygen to breathe in the air, but the unique location makes Concordia station in Antarctica an attractive place for scientists to conduct research. The aurora australis that adds colour to this picture is a well-deserved bonus for the crew of 13 who are spending the winter months cut off from friends and family. Image credit: ESA/IPEV/PNRA–B. Healey, CC BY-SA 3.0 IGO

As you crank up the strength of the solar storm, the auroras become visible to more and more of the planet. The Carrington Event’s aurora were visible for three nights, and not just in the North. There are records of people seeing the aurora from New York all the way down to New Orleans, and from many cities in between. And it didn’t stop there - Jamaica and Cuba were also in on the show. In fact, the more you dig into historical records, more and more of the planet appears to have seen the light show in the sky. In 2015, a paper digging into historical records in South America found a record of a bright, S-shaped light in the night sky, which woke up the people living in a town in Columbia. Columbia is only 8 degrees north of the Equator, which means that if they could see it, a huge fraction of the planet was likely exposed to the auroras if their skies were clear.

There are records of a golden or fiery red aurora in China and Japan from the same solar outburst; a number of diary & local news accounts tell of a strange sky that evening. To be specific, the main “Carrington event” is considered to be the main wave which hit the planet while it was nighttime for the Americas and Europe, but there was a bit of a second wave, which hit during the night for Asia.  Unfortunately, it appears to have been cloudy in Korea, and possibly cloudy over the middle of Japan as well - the most spectacular light show yet recorded can still be stymied by clouds. (Ask anyone who tried to watch the solar eclipse in the UK in 2015 through thick cloud.) From Japan, the auroras appeared to be a massive fire on the horizon - and many of the writers appeared to have been waiting for news of a giant fire which never materialized.

ESA astronaut Tim Peake posted this stunning image on his social media channels, commenting: "Station passed through magnificent aurora Australis last night." Image credit: ESA/NASA CC BY-SA 3.0 IGO

ESA astronaut Tim Peake posted this stunning image on his social media channels, commenting: "Station passed through magnificent aurora Australis last night." Image credit: ESA/NASA CC BY-SA 3.0 IGO

The aurora would be the least of our concerns if another Carrington-sized solar storm hit us. Auroras are the glow of ionized gas in our atmosphere, the result of a severe bashing by an influx of charged particles from the Sun. Because there’s so many charged particles moving around, they induce a current on wires below them. And this induced current is under no obligation to be small and manageable. In 1859, this meant that people’s telegraph equipment was shocking them, or working even though it had been unplugged, or not working at all.

We use a lot more electronic equipment than we did in 1859. We have a lot more GPS and communication satellites now, which underpin everything from your cell phone’s ability to check the best path between you and your home, to your plane’s ability to track itself through the sky, to some credit card purchases. And, as a solar storm which impacted Quebec in 1989 proved, our power grids do not like extra current; Quebec’s power grid (which has since been improved, I should note) went down in 90 seconds and stayed down for 9 hours, keeping millions of people out of power.

Fast-moving protons from a solar energetic particle (SEP) event cause interference that looks like snow in these images from the Solar Heliospheric Observatory taken on January 23, 2012. Image Credit: ESA&NASA/SOHO

Fast-moving protons from a solar energetic particle (SEP) event cause interference that looks like snow in these images from the Solar Heliospheric Observatory taken on January 23, 2012. Image Credit: ESA&NASA/SOHO

The US in particular is generally considered to be very poorly prepared for the sort of electrical damage that a power surge from a strong solar storm could impose. A report from the National Research Council, produced in 2008, estimates that a Carrington-style event would put more than 130 million people out of power, which, given the population of the US at the time, means that 43% of the population of the US would be out of power.  They estimate that $1-2 trillion dollars would be lost (either through cost of replacement or via people not being able to work), which would take 4 to 10 years to recover from.

A “best-case” scenario for weathering a giant solar storm means lots of backup systems in place for our power grids, the ability to handle sudden weird influxes of power, and the monitoring power to know when they’re coming. This requires a healthy set of satellites monitoring our Sun - we’ll only ever have a few day’s warning, but it’s better than no warning - we might be able to set satellites into safe mode, make sure the power grids are able to handle it, and switch off non-vital electronics that can’t handle it.

Astronaut Scott Kelly posted this photo of an aurora taken from the International Space Station to Twitter on August 15, 2015 with the caption, "Another pass through #Aurora. The sun is very active today, apparently. #YearInSpace". Image credit: NASA/S.Kelly

Astronaut Scott Kelly posted this photo of an aurora taken from the International Space Station to Twitter on August 15, 2015 with the caption, "Another pass through #Aurora. The sun is very active today, apparently. #YearInSpace". Image credit: NASA/S.Kelly

As nice as it is to dream about a theoretical, bright, planet-wide aurora (from an aesthetic perspective), the reality of those aurora mean that they are harbingers of large scale electronics failures, both on the ground and orbiting above us.

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How do Coronal Mass Ejections happen, and how do they affect us?

A Coronal Mass Ejection, or CME, is when the sun suddenly releases a lot of matter and energy from its surface, flinging it outwards into space. To understand why it would do this, we need to know a bit more about how the surface of the sun works.

The Sun is a miasma of incandescent plasma, and it rotates around its axis once every 30 days (roughly). But because the sun isn’t a solid body like the Earth, the entire Sun does not have to rotate at the same rate. If the equator of the Earth tried to rotate faster than the poles, the rocks that make up the surface of our planet would have to shear apart. But because the Sun is just gas, it can have an equator that rotates a few days faster than its poles - a gas doesn’t have the same resistance to shear as rock does.

The Sun also has a pretty intense magnetic field, which normally would start at the top pole, and travel smoothly downward to the bottom pole, as it does on the Earth. However, since the equator of the Sun is travelling a little bit faster than the poles, the magnetic field gets dragged along with the faster material, which pulls the magnetic field into a twist. After enough twisting, the magnetic field begins to form little loops that pop out of the surface. You can replicate this effect by taking a bit of string or cable and twisting it - at some point, the cable will want to make a twisted loop if you give the line some slack. These little loops tend to be associated with sunspots.

As the years go by, the magnetic field of the sun gets increasingly twisted, and these loops get bigger and more common on the surface of the sun. As the magnetic fields get increasingly tangled up in themselves, if the bases of the magnetic fields (or, in our cable analogy, some of the cable closer to your hands, not in the loop itself) touch, they snap together and create a new magnetic line, without the loop. This then leaves the loop in the lurch - but it doesn’t just hover over the surface of the sun. The ‘snapping’ together generates a lot of energy, which is all dumped into flinging the material which was trapped in the loop outwards, into the solar system.

These particles have extremely high energies, which means they leave the sun’s surface at an extremely high temperature and at an extremely fast pace. Since these can occur at any point on the Sun’s surface, (although they don’t tend to form at the exact poles, since the magnetic field doesn’t get very twisted there) and and the Sun is constantly rotating, the probability of a CME being headed straight for the Earth would be pretty low, if they shot directly out from the surface. However, CMEs are notable because they eject particles over a wide swath of space, so our odds of running into this stuff is much higher than you would expect. So what happens when they head for us?

Fortunately, the Earth’s magnetosphere takes the brunt of the blow from these particles. The magnetosphere can be thought of as a giant magnetic shield, deflecting charged particles that come our way. This protects us from most of this kind of radiation from the sun. Our magnetic field sinks into the planet at the magnetic north and south poles (close to, but not exactly the same as, the rotational north pole). This means that there’s a bit of a divot in our magnetic field, and particles can get stuck in here, and go around bombarding the atmosphere with radiation, causing the atmosphere to glow. This is what causes the Northern and Southern lights - also known as the aurora. If you’re in the far north and you hear that there’s a solar storm coming, head outside when it hits - there’s a good chance of seeing the aurora any time a CME comes our way.

Less aesthetically pleasing is the fact that CMEs can do a fair amount of damage to some of our satellites in orbit. Satellites are built to be able to handle slightly more than an average amount of radiation under normal circumstances. But if we’re getting hit with the kinds of energies that CMEs bring, even after 93 million miles, some satellites can’t handle the dosage. The constant bombardment of the satellite by charged particles can cause the satellite itself to become charged. This is very similar to becoming electrically charged by shuffling around in socks on carpet. If the satellite gains enough charge, it can short-circuit itself, which will kill the satellite, if a crucial part fails. (In space based satellites, most parts are crucial.) This kind of thing mostly affects satellites that are in very high, particularly geocentric orbits, like GPS satellites. The International Space Station is usually unaffected since it’s in a lower orbit, although in the case of strong storms, the astronauts can take shelter in more highly shielded portions of the the ISS.

On the surface of the Earth, most of the time the most noticeable part of a CME is the aurora; most of the other consequences of a coronal mass ejection just don’t make it to the surface.

That said, in 1989, a solar storm knocked out power to 6 million people living in Quebec because there was so much turbulence in the magnetic field of the Earth that it induced a current in the power lines, and overloaded a set of circuit breakers. In the face of extremely large coronal mass ejections, we can have problems on Earth. Fortunately, as long as we have telescopes observing the sun, we will always have several days warning.

Have your own question? Curious about something I wrote here? Feel free to ask!