TRANSCRIPT
Earth has experienced its largest solar storm in over twenty years.
Extraordinary colour displays lit up the sky across the world, stunning everyone who managed to catch a glimpse of the rare but spectacular show.
The aurora borealis and aurora australis, also known as the northern and southern lights, are more commonly seen on a much smaller scale.
The southern lights, when they occur, are usually only visible from Tasmania and parts of New Zealand.
The far more famous northern lights are usually only visible from parts of northern Europe and Canada.
But in mid-May the spectacular curtains of purple and green light graced skies as far as Queensland in Australia, as far south as Spain in Europe and all the way down to Florida in the United States.
So, why did it happen?
Well, it has everything to do with solar weather, magnetic fields and far-flung particles from the sun.
Astrophysicist, Cosmologist and research fellow at the Australian National University, Brad Tucker with more on what this really means.
"The sun goes through periods where you get lots of activity, and during these periods the sun is prone to eruption. so, these eruptions attract a whole bunch of gas, heated gas, which is plasma, and this travels through space. Now it's an electrically charged so as it travels through space, it slams into the magnetic bubble of the earth and slams into the Earth's atmosphere and what it does, it excites the gas in Earth's atmosphere causing it to glow and that's what happened over the weekend. "
We often think of the sun as a solid object, in reality, it's more like a really hot ocean with layers of molten plasma being pushed around by the sun’s magnetic fields.
Have a listen to this.
What you're hearing is the sound of the sun, captured by NASA, and those low humming sounds are caused by the constantly moving particles.
Like on Earth, there are several layers to the sun, and from time to time the northern and southern parts of the sun spin a little faster than the middle.
The friction caused by that churning molten plasma can lead to charged particles being tossed into space - and it's the speed of those particles that causes an aurora.
Dr Tucker says that like on Earth, some solar storms are simply larger than others.
"This was a fairly large storm. We don't usually get storms this large the last one was probably about 20 years ago in terms of power and intensity, just like storms on earth you sometimes get that rare really big storm. It's the same in this case that was a large enough storm, and so a lot of energy and that travelled through the Earth's atmosphere, creating the Aurora, really into far northern parts of Australia that generally don't see it so that was kind of unique combination of storm intensity to create those conditions."
The reason this solar storm was so big is linked to the scale and number of what are called a Coronal Mass Ejections.
This type of solar storm rips millions or billions of tonnes of plasma from the sun's atmosphere, catapulting them into the solar system at speeds of up to nine million kilometres per hour.
Nour Rawafi is from the Johns Hopkins Applied Physics Laboratory.
"What happened during the last few days, a system of very complex sunspots that came together and formed a huge, active region of the sun. And these are extremely active in the span of a day or a day and a half. They launched, I believe something like seven coronal mass ejections."
Luckily for us, Earth's atmosphere protects us from the storm by absorbing and deflecting the blast well before it reaches the surface.
The Earth's own magnetic fields deflect particles towards the North and South Pole, hence the higher likelihood of seeing auroras in areas further from the equator.
Whilst much of it is somewhat random, there are periods of time in which solar storms occur more frequently.
Dr Tucker says this is to do with what's called the solar cycle.
"The sun goes through this 11 year period where it has a maximum and minimum in terms of activity and we're in that maximum now. And so when you have these periods of maximum activity, the sun generates more storms and more severe storms, just as any other weather system, you know bushfire season and cyclone season. "
Space scientist at the National Oceanic and Atmospheric Administration Space Weather Prediction Center, Robert Steenburgh says one region has been particularly active.
“During this time in the 11-year solar cycle, we're coming up towards solar maximum. So there are a lot of sunspot regions on the earth-facing side of the sun. And one of these large regions was possessing, perfectly producing flares and associated, what are called coronal mass ejections - big blobs of the solar atmosphere that actually get ejected from the sun into interplanetary space. So this region has been producing lots of the solar flares, particularly strong ones and ejecting blob after blob of plasma of the solar atmosphere aimed at Earth.”
Massive blobs of the solar atmosphere moving at extreme speed towards Earth sounds like something we should be terrified of.
In reality, most solar storms, even of this scale, hit earth with little more than a light show.
Dr Tucker says the colours visible from Earth depend on what gas is charged or excited by the currents.
"You can think of that as we have lots of nitrogen and oxygen in our Earth's atmosphere, and there are different layers so depending on how much energy there is in which layers reach will determine that colour the greens and kind of pinks usually come from oxygen and the more purple or darker red colours come from nitrogen. So that's the gas that is really being excited and charged by the storms and glowing."
Professor of Space Physics at the University of Reading, Matthew Owens says the auroras work similarly to how a neon light works.
“You run an electrical current through a gas and you get it to emit light. But the reason we’ve got these electrical currents flowing through the atmosphere is because the earth’s own magnetic field is being, as you say, battered by these eruptions from the sun that left about three days ago."
Aside from the spectacular displays, solar storms at this scale can also cause technological issues.
But Dr Tucker says it's rare for these to have major impacts.
"For the most part, most of this energy is absorbed by the Earth's atmosphere and this magnetic protective layer, the magnetic field so we don't have that many effects on earth now if there is even more than what we saw over the weekend, there could be enough energy that does reach the surface. And because it is electrically charged, it can create some interference the usual cases it creates kind of a bit of electrical static, charge in the Earth's atmosphere so sending radio signals can get interfered. It has a lot of interference are satellites that's usually the biggest worry."
The largest solar storm in human history lasted several weeks in 1859 and is known as the Carrington Event, after the amateur astronomer who first connected the solar flares with the technological disturbance.
The Carrington even wreaked havoc on telegraph systems, with reports at the time of sparks showering from telegraph machines, operators receiving electric shocks and papers set ablaze by the rogue sparks.
But a few hundred years ago, the earth was not covered in millions of kilometres of wires carrying electricity.
If a solar storm of that scale were to happen today, experts say it could cause a shutdown of power grids, causing blackouts for weeks or even months.
Robert Steenburgh says centres like the NOAA and Australia's own Space Weather Prediction Centre exist to ensure we know if there's anything to worry about.
“You know, by making folks aware of space weather and by having a facility that, that's our job, we keep an eye on this stuff and let people know again, there are ways to try and mitigate and work around some of these things. So, if everything's going right, you won't notice a whole lot other than the aurora. That's the gift from the sun. But you know, the rest of it, with any luck, will be pretty low profile, at least to the average person.”
