The Secret Life of the Sun

90 million miles from us

is the power that shapes our world.

Our very own star.

The sun.

We see it shine in the sky above us.

But beyond our sight, something dramatic is happening.

The sun is going into overdrive.

Our star is more active now

than it's been for a decade.

It's sending eruptions of superheated plasma

and vast waves of radiation towards our planet,

with the potential to disrupt our lives

in completely unexpected ways.

At the same time, a new generation of satellites

is showing us the sun in more detail than ever before.

It's almost pulsating.

I'm Kate Humble.

And I'm Helen Czerski.

Together, we're going to unravel what's happening to our sun.

From Britain's leading centre for solar research,

we'll use the latest satellite images and a team of world-class experts

to decode the sun's inner workings.

Something in the sun's atmosphere snapped.

We'll explore the sun's most spectacular displays.

I love your laboratory, it's brilliant!

Investigate its mysterious cycles of activity.

-So it took seconds to get from the sun to the satellite.

-That's right.

And discover how our sun is behaving right now.

70 miles west of London lies Britain's answer to NASA.

This is the Rutherford Appleton Laboratory in Oxfordshire.

At RAL, satellite instruments are designed and tested

before they're launched into space.

And scientists are analysing the latest information

these satellites beam down around the clock.

It's one of the most important

centres of solar research in the world.

We've set up inside one of RAL's giant research facilities

so that we can talk to some of Britain's leading solar scientists

and see for ourselves

the extraordinary images they're using to study our star.

We can't look directly at the sun without damaging our eyesight,

but a new fleet of satellites are allowing scientists here at RAL

for the first time to get a unique picture of the sun.

In 2006, NASA launched the twin STEREO spacecraft

to observe the sun from two sides simultaneously.

The Solar Dynamics Observatory followed four years later.

It's able to visualise the sun in high resolution for the first time.

These satellites show the sun

as far more than simply the burning disc in the sky that we see.

Here at RAL, head of space science Richard Harrison

is responsible for analysing those images.

So, Richard,

how are these new satellites advancing our knowledge of the sun?

Well, the whole point is that we have now built up

a fleet of spacecraft, an international fleet of spacecraft,

that are really studying the sun in phenomenal detail.

We can see the sun from both sides.

We can see a complete star, and we'd never done that before.

And these satellites can detect types of light from the sun

that are invisible to the naked eye.

The brighter regions here are what we call active regions,

and they're regions a bit like volcanoes and earthquakes

on the Earth, if you like, regions where the sun is active,

and there's a lot of interesting stuff happening in here.

You can see it with your own eyes, it's so complex,

it's moving all the time, like a plate of writhing spaghetti.

And I mean, this is an extraordinary image.

We can see several colours put together,

showing you the full complexity in all of its glory, if you like,

the truly complex atmosphere writhing in front of your eyes.

And this sort of illustrates it, puts it in a nutshell,

how fantastic it is to be studying the sun

as it approaches a peak in activity

with this wonderful fleet of spacecraft.

This peak in activity is known as a solar maximum.

It's the high point in a cycle

the sun goes through on average every 11 years.

From relative calm...

..to intense activity...

..and back again.

A cycle that's fundamental to how the sun works.

Understanding this solar cycle

will help us discover the secret life of the sun.

But for most of us on Earth,

the sun is something we rarely examine in any sort of detail.

To begin to understand its extraordinary power

and its changing cycles of activity, we need the help

of one of the most dramatic events in the astronomical calendar,

a total solar eclipse.

And to see that, I had to travel to the other side of the world.

November 2012.

I've come to Cairns, Australia.

I'm joining people from across the globe

because in 48 hours, there's going to be a total eclipse.

But this one is special

because it promises to reveal something crucial about our sun.

Cairns is a relatively small town in Australian terms.

It's home to about 130,000 people.

But that number could swell by as much as 50,000

in the next couple of days, and all for an event

that's going to last just two minutes and two seconds.

It's an emotional experience, it's a lovely way to sort of see the world.

Everyone is happy. It's fanta... It's a natural spectacle of science.

I'm getting excited, yeah!

I've never seen a total eclipse before

and we've got our glasses, and we're all set to go.

We've got our fingers crossed for clear skies.

You can't safely view an eclipse

unless you have glasses with powerful filters.

-Hi.

-Hello.

-That's what I'm after.

-The very last pair.

-No way!

-Three dollars.

-Did you want some as well?

-Oh, yeah, we've been searching everywhere!

-This is the very last pair in Cairns.

-I'm really sorry.

-Oh, you're joking!

-We could share them.

Don't film this. This is horrible. This is like breaking my heart!

No...

It's once every 50 years or so, so make the most of it.

-Thank you very much.

-Thanks, bye!

-Seriously, your last pair?

-Last pair. No more, all gone!

To get an eclipse, the moon must drift between the sun and us.

At what's called first contact, the moon begins to block it.

But what's extraordinary

is what happens when the sun is completely covered.

That moment of totality

reveals something that's normally hidden by the sun's glare -

the sun's faint atmosphere, the corona.

And it's the corona that's key to what this eclipse can tell us.

The corona is due to reveal itself at precisely 6.38 in the morning

the day after tomorrow.

But the fact that we get total eclipses in the first place

is thanks to an astonishing coincidence.

Earth is the only planet in the solar system

from where you can witness a total eclipse,

and the reason for that is down to pure luck.

The moon is 400 times smaller than the sun.

But it's also 400 times closer to the Earth.

So when the moon's orbit brings it between the Earth and the sun,

it appears to be exactly the same size as the sun,

and it's able to block out its entire surface from our view.

There's a total eclipse on average every 18 months,

so they're not exactly rare.

But catching one isn't easy.

The narrow shadow paths they trace on the Earth's surface

are far more likely to pass over uninhabited regions,

such as the oceans, than a populated area like Cairns.

And the timing of this eclipse is significant.

Right now, we're due to be at solar maximum,

the period of greatest activity in the sun's cycle.

But each maximum is slightly different,

so scientists need to confirm that we have actually reached it.

One way to do that is to study the sun's corona during totality.

Click on that.

'And that's what makes this eclipse especially exciting.'

Delivery!

Jay...I think we've got the box you wanted.

'Even to the most hardened eclipse chasers.

'Astronomer Francisco Diego has seen 17 total eclipses.

'This time, he's advising a group of a hundred British eclipse chasers.

'But he's also brought his own equipment.'

The sun, as far as it is...

You're not the most hi-tech scientist I know!

This is an ideal container for a very delicate part of equipment.

You're like a Blue Peter scientist, it's brilliant!

-Can you hold this for me? Careful with the wind.

-I've got it, yeah.

'A camera and some home-made filters

'are all he needs to take detailed photographs of the corona.'

So what I do, I remove the lens cap here...

'And it's the shape of the corona in his photos

'that will tell Francisco if we're at solar maximum.'

So the eclipse gives that opportunity to admire

and to study the outer layers of the solar atmosphere.

These layers, the chromosphere and the corona,

are an indication of solar activity.

The shape of the solar corona is changing all the time.

For example, when the corona is very round,

that means the solar activity is at a maximum.

Francisco will have only two minutes

in which to get a successful picture of the corona.

THUNDER RUMBLES

But that brief window of opportunity

is threatened by a more familiar force of nature.

Cover the telescope!

Oh, man!

The eclipse is tomorrow morning

and the forecast is not looking good.

This is tropical Australia, we're going into the rainy season,

and the weather could obliterate the old thing.

2am, the day of the eclipse.

I'm following Francisco and his eclipse chasers

inland from Cairns to get away from the rain clouds.

We have to reach clear skies before dawn,

or we'll miss the eclipse.

We've pulled off...the road, finally.

It's...ten past five.

And the sky is lightening dramatically quickly.

Sunrise is going to be... in about half an hour,

and first contact...

-Follow me, quick!

-OK, OK.

..and first contact is ten minutes after that.

Wow!

That's incredible.

The sun has just made an appearance...

..above the clouds...

..and it's got a chunk

out of the top left corner.

The moon has begun to block the sun,

but the sun is so bright

that we won't notice any darkening of the daylight

until it's almost completely covered.

What do you think, Francisco? It's looking quite skinny now.

It's quite skinny, yes, about ten minutes before totality,

so this is where things are going to happen faster and faster.

The darkness is going to really come much quicker.

You... You feel it, it's physical.

And it's sort of terrifying, actually!

-HE CHUCKLES

-Isn't it?

-It is!

I mean, just look at it. It's just...

Every moment you can feel the light just dropping and dropping.

It's like somebody's stealing the sun.

And it's now just a tiny...

-..hair's breadth in the sky.

-Yeah, two minutes, two minutes to go.

And it's so cold, the temperature has just completely dropped.

It's like everyone's collectively holding their breath.

SHE GASPS

Oh, my goodness!

SHE LAUGHS

OBSERVERS CHEER

It's the most amazing thing!

SHE LAUGHS

I can't believe how beautiful it is!

Oh, amazing!

The moon has completely blocked the disc of the sun.

A delicate halo is all that remains.

It's the corona.

Francisco now has two minutes and two seconds

to get the photos he needs.

Here it comes!

CAMERA SHUTTER WHIRRS

It's ridiculous! I...

Isn't that amazing?

Amazing.

It was worth getting up at two o'clock in the morning.

HE CHUCKLES

Absolutely worth getting up at two o'clock in the morning!

I challenge anyone to watch a total eclipse without being deeply moved.

It's a glimpse into the hidden workings of the sun.

It makes you kind of look at it in a slightly different way afterwards,

-doesn't it?

-Absolutely, yes.

Somehow, you can't take it for granted any more.

No, you cannot, and then... Well, life on Earth depends on it,

has depended on it for billions of years, really.

That was the first time I've ever seen a total eclipse.

But what has the corona revealed?

Has the sun reached solar maximum, its peak of activity?

Back at RAL, we can now get the answer from Francisco's photographs.

An eclipse is a fabulous thing to experience,

but there was a scientific reason for taking those photographs.

-So are we at solar maximum?

-It looks like we are.

We have pictures taken in solar minimum.

For example, this one, that was taken in 1994, two cycles ago,

when the solar activity was at a minimum.

-Can you see an axis here?

-Really clear, isn't it?

Yeah, the sun is very orderly, very steady, very quiet.

-There's a very clear pattern.

-By contrast, last year in Australia

we saw the corona in a completely different way.

This is the picture we took there. Now, tell me where is the axis.

It's just the same all the way round, isn't it?

It's all over the place, it is all over the place,

Because the solar activity has blown the corona in all directions.

The sun is extremely dynamic here.

So this is an interesting time to study the sun.

Very, very interesting.

We are very excited about solar maximum,

and then again the sun will come...

in the next years will come down to a quiet stage,

and then this whole cycle repeats every 11 years.

So what causes these solar cycles?

To understand, we first need to know what's going on deep inside the sun.

It's a place we can never go,

but we can learn a lot from something that makes the journey

all the way from the core of the sun to us here on Earth.

Sunlight.

Sunlight, the light from the sun.

We take it completely for granted.

But it's still mysterious.

Where did it come from? How did it get here?

We think of sunlight as simply coming from the sun's surface.

But its journey begins deep within our star.

And what makes sunlight's journey so epic is the sheer size of the sun.

The mass of the sun is 2 followed by 27 zeroes,

that is the mass of sun in tonnes.

And so that makes up 99.85% of the entire solar system.

The solar system is basically just sun

with a few little fragments circling round the outside.

And it's the sun's enormous mass

that creates the conditions to produce sunlight.

Its intense gravitational pull forces the sun into layers,

each with its own special properties.

Beneath the thin outer peel is a 200,000-kilometre thick layer,

where hot material rises and falls.

The layer underneath carries the sun's heat outwards.

And around 550,000 kilometres down is the core,

a 16-million degree furnace.

Here, the entire mass of the sun is pushing inwards,

exerting vast pressure.

And this is where sunlight is born.

To understand how that vast pressure creates sunlight,

I've come to the National Ignition Facility, NIF, in California.

Sunlight exists because of a process

going on deep in the core of the sun called fusion.

And what's happening there is that the pressures and temperatures

right in the middle of the sun are so enormous...

..that hydrogen atoms can fuse together.

And when that happens,

a tiny, tiny bit of mass is converted into a huge amount of energy.

And that little process is the key to a star like our sun.

Without that single process, the sun would be a cold, dead star

and the Earth would be a cold, dead planet.

So the key to the behaviour of the sun

and to life on Earth

is fusion.

I'm about to see how the scientists at NIF

are trying to make a tiny sun and recreate fusion.

All this is about getting ignition that could change the world.

Here, in this dust-free environment,

Beth Dzenitis creates hydrogen fuel capsules

smaller than a grain of rice

and destined for a very violent fate.

This is called the capsule fill-tube assembly.

It's a two-millimetre diameter plastic capsule.

192 laser beams converge on the capsule,

and that plastic material blows away from the capsule

when it gets hot and under high pressure.

And that causes a subsequent reaction of the fuel there

to be compressed so that the hydrogen atoms fuse.

To get those atoms to fuse,

they need to generate similar pressures to those at the sun's core,

340 billion times the pressure on Earth.

It's a tall order.

But there is a way.

The 192 individual laser beams they use

are each more powerful than any other laser on the planet.

And they all fire at a spherical chamber at the heart of the complex.

This is the target chamber,

and when the lasers hit the fuel capsule at its centre,

they bring the atoms together with the same force as in the sun's core.

But to truly mimic our star,

the NIF team needs to pull off an even greater trick.

Proceeding to system shot countdown state.

Once ignited, the fusion reaction must keep itself going.

Starting system shot sequence on my mark.

Three, two, one, mark.

May I have your attention?

Preparations for shot operations in laser bay two are under way.

Leave laser bay two now.

It's not without its dangers.

Before every shot, the area is evacuated.

Steel and concrete doors a metre thick enclose the target chamber.

A misfire from the most powerful laser in the world

could cause a catastrophic explosion.

MOR ready for system shot countdown clock.

And even the smallest fusion reaction

unleashes a lethal blast of neutrons and high-energy light.

..Three, two, one.

The only visible sign

is this flash from the world's biggest laser as it fires.

But inside that fuel capsule,

they're hoping to create a tiny sun

and with it, man-made sunlight.

Another day, another shot.

The NIF team routinely achieve short-lived fusion.

But today, still no self-sustaining fusion.

Yet if we could achieve it on Earth, we'd have the sun's energy on tap.

Recreating a small sun in this target chamber

that's not too far away is always... daunting, in a lot of respects.

We will get there eventually.

It's that elusive trick of generating endless energy

that makes our sun so miraculous.

The result is the birth of sunlight in the sun's core,

in particles of light energy known as photons.

But their journey is far from over.

Imagine this pinball is a newly created photon.

That light must now reach the sun's surface.

And that is a really complex and difficult journey,

because in-between the core of the sun and the surface

there is a seething mass of stuff that we call plasma.

Like my pinball dodging the flippers and bumpers,

the photon now has to navigate through that plasma.

But my pinball - or photon - can't take a direct route out.

It's forever colliding with particles of plasma

moving at thousands of miles per hour.

And with hundreds of thousands of miles of plasma to cross

between the sun's core and its surface,

a journey that should take two and a half seconds at the speed of light

takes much, much longer.

Even though it's travelling at the speed of light,

as fast as anything can go,

it's still estimated that it'll take 10,000 to a million years

just to get from the core of the sun to its surface.

And then...freedom.

What we think of as sunlight's journey,

the 90 million miles from the sun to the Earth,

is only the last eight minutes

of an odyssey that could have taken thousands and thousands of years.

It's...lovely, fantastic,

to think that this gentle light that's touching me now

started off in a violent, dramatic beginning

right in the centre of a star

and then spent 100,000 years finding its way out of that star,

and finally spent just eight minutes

travelling as fast as anything in the universe can travel,

the speed of light, to get to me here.

But this extraordinary journey raises a question.

Fusion in the core never stops.

So why does the sun's activity go up and down

with the 11-year solar cycle?

Back at RAL,

that's one of the questions that interests solar scientists.

The key lies in how the fusion reaction affects the sun's plasma,

that seething mass between the core and the surface.

To explain why this leads to solar cycles,

we've been joined at RAL by solar physicist Lucie Green.

The heat generated by this reaction inside the sun,

it heats up the gas and, in fact, it superheats it,

so the gas is... the particles of gas are torn apart

to form a plasma.

Just as the hot air in the room around us is rising in packets,

so the gases in the outer layers of the sun do the same thing.

This is called convection.

So gases get heated from below

and they rise up to the surface of the sun.

But because this gas, the plasma, is so hot,

it's also electrically charged.

So as it moves up and down with the convection currents,

it creates powerful magnetic fields.

And that's not all.

The sun, like the Earth, spins on its axis,

so plasma also flows sideways.

Which has a dramatic effect on those magnetic fields.

You start to see the magnetic field lines being wound up,

and eventually it becomes so strong that the magnetic fields rise up

and penetrate the surface of the sun,

and that's when we have the build-up to solar maximum.

At times of solar maximum,

those magnetic loops break out from the surface of the sun,

drawing the sun's plasma with them.

This one loop is many times bigger than the Earth.

But the sun doesn't stay like that.

Eventually, the magnetic fields disperse

and they rearrange themselves,

and we go back to solar minimum again,

where you have the nice ordering of the magnetic field.

It does this every 11 years,

and though the sun may be 90 million miles away,

this cycle matters to us here on Earth.

What is the implication of times of solar maximum for us on Earth?

What do we experience?

Well, the sun is constantly expanding out into space.

Its outer atmosphere, with the magnetic field,

-is being drawn out into something that we call the solar winds.

-Yeah.

Now, at times of solar minimum, the wind is fairly, erm...ungusty,

-it flows quite slow.

-Quite light.

-Quite light!

But at solar maximum, the magnetic fields start to get more complex,

and that leads to vast streams of solar winds coming our way.

The solar wind is a constant stream of particles

flowing out from the sun.

It bombards the Earth.

Most of it is deflected by our planet's own magnetic field.

But a small amount of its energy does get through,

with extraordinary effects.

Effects I'd always wanted to see for myself.

If you want to see this evidence on Earth of solar winds,

you need to head right up

into areas that are cold, rather sunless and rather dark.

This is Lapland in Arctic Sweden.

It's February,

it's minus 19,

and a long winter's night is about to fall.

I'm here to see an old friend.

She's an extraordinary woman who, 15 years ago,

left her home in Birmingham and came to live here permanently.

And all because she became bewitched

by the strange and astonishing phenomenon

that I'm hoping to witness too.

It's called the aurora borealis,

also known as the northern lights.

The aurora is the solar wind made visible on Earth.

As the wind encounters our planet's own magnetic field,

it sends energy down the magnetic field lines towards the poles,

causing our atmosphere to luminesce in ghostly colours.

Right now at solar maximum is the best time to see the aurora.

But I still need a cloud-free, moonless night.

My friend, Patricia Cowern, knows the challenges.

She's photographed the aurora countless times.

-Wow, so that's above here, isn't it?

-It is above the house, yes.

That's one of the early ones

that I took when I very first started northern lights photography.

-Oh, my goodness!, Look at that!

-This is where we're sitting now.

-Really?!

-Yeah.

You see, I just think I'm going to pop with excitement

if I see a sky that looks like that.

When we go out this evening, am I going to get to see them?

Hopefully!

If we can get rid of the clouds.

-We have the darkness, we actually do have activity at this moment.

-Right.

So what we need is for these clouds to go away.

OK, well, I'm going to get outside...

-And start blowing.

-Yes!

Near the poles, there's a ring-shaped zone

where our atmosphere is most affected by the solar wind's energy.

Lapland is slap-bang in that zone,

which is why it's such a hotspot for the aurora.

My first attempt to see it.

To the naked eye, it's very faint.

But with time-lapse cameras,

we can see there's definitely aurora going on up there.

But although there's no moon to spoil it,

there are clouds in the way.

Well, it's coming up to 11 o'clock at night

and the cloud is still stubbornly hanging around.

There's a few breaks in it.

I've had sort of tantalising glimpses

of wisps of green smoke across the sky,

but nothing like the scale that we know that they're capable of.

I have one more night before the moon returns

and wrecks my chance of getting a clear view.

But it's not just sightseers like me who are drawn here.

-I love your laboratory, it's brilliant!

-Isn't it?

'It's a perfect backdrop for scientists like Gabriela Sternberg.

'She's interested in an important question -

'how well is our magnetic field holding up

'to the constant battering of the solar wind?'

So, let's use this nice snowball to demonstrate this.

-So if this now is the Earth...

-Yeah.

..and we have the sun, the beautiful sun, over here,

-so from the sun now comes solar wind.

-Yeah.

And at some point, it encounters the magnetic field of the Earth.

Most of the solar wind now goes around, like this.

How powerful is this solar wind? I mean, obviously, we can't feel it

because of all these layers of protection,

but is it gale force? Is it like a hurricane?

What happens is, it comes particles, and they come very quickly,

-so they move with the speed of, like, 400 kilometres per second.

-Wow.

So they move really, really fast.

So you get this gigantic shock wave where the solar wind slows down.

This boundary separating us, or our space, from the solar wind,

it's very, very, very, very thin.

It's like a thin, almost transparent, veil

separating us from this blowing wind, from the solar wind.

And that, we think, is really cool.

How can these really thin boundaries, how are they formed?

And why are they so thin?

So the aurora is but a faint trace of the solar wind's true strength.

Out there is a violent collision where it meets our magnetic field.

That thin shell gives us vital shelter.

Last night in Sweden.

It's tonight or never.

It's about...minus 30 outside,

and it's absolutely clear, it's been clear all day.

So we're going to go out and see what's happening.

Oh, my goodness, look at those stars.

It's so clear!

Oh, my goodness, look at that!

Look what's happening in the sky!

With ordinary cameras, you can see it faintly.

But it's with the time-lapse cameras that we can capture the full glory.

Look at that, it's just...spanning the whole of the eastern sky,

like a giant sort of green rainbow.

Under this balaclava, I am grinning like the Cheshire cat.

-It's mesmerising, isn't it?

-Beautiful.

You can't kind of take your eyes away from it.

The aurora is a stunningly beautiful display of the solar wind,

but also a reminder of its enormous power

and the protection we get from the Earth's thin magnetic shield.

So what would happen

if we were ever exposed to the full force of the sun?

It's a question that the scientists back here at RAL

have been studying intently.

The solar wind is a mere hint of the vast amount of radiation

and particles that the sun sends our way.

It's known as solar weather,

and its impact on Earth can have a more alarming side.

Richard Harrison, head of space science at RAL,

is an expert on its most violent form, solar storms.

So, Richard, we know that the Earth is protected

from the full force of solar weather by the Earth's magnetic field,

but is there any danger that that magnetic field could be breached?

Well, the best way to answer that

is actually to look back at the sun's atmosphere again

and these wonderful magnetic loops in the sun's atmosphere,

like elastic bands sort of writhing around, being tied up in knots.

And you might expect occasionally something might break,

so in these regions you see here, that happens.

This image here is actually from helium in the sun's atmosphere,

and you see a huge cloud erupting there.

That's a billion tonnes of mass from the sun being ejected into space,

so something in the sun's atmosphere just snapped.

These gigantic solar storms are called coronal mass ejections.

They are the most high-energy events in the solar system

and the sun unleashes more of them at solar maximum

than at any other time.

They can hurl clouds of plasma towards us at alarming speeds.

To cover the 90 million miles from the sun,

seen here reduced in scale on the right,

to the Earth on the left

can take less than a day.

And as Helen found out,

they have the power to overwhelm the Earth's defences.

Solar storms can destroy satellites,

silence communications,

ground aircraft.

Order up!

But the link they threaten most in our modern lives

is our dependence on electricity.

If you have any doubt, take a look at this booklet.

It's published by Lloyd's of London, who are insurers,

and they wrote it with the Rutherford Appleton Laboratory,

and I think one of the most interesting sections

is where it lists the potential impacts

that disruption to the power supply would have.

And this is important, because our power grid is one of the things

that's most vulnerable to a big solar storm.

The highly charged particles of coronal mass ejections

can induce powerful electrical currents on the Earth's surface,

overloading circuits and melting transformers.

And the reason it matters so much is that everything is interconnected.

And so if we lost power, we'd not only lose lighting and heating

and the ability to cook our food.

We also, for example, lose our fuel,

because pumping stations rely on having electricity

to pump the fuel out of their reservoirs.

Sanitation, water supplies, communication systems.

We know we're vulnerable because we've been hit in the past.

In Quebec, the entire power grid went down after a solar storm in 1989,

plunging millions into freezing darkness.

But we're not helpless.

There are precautions we can take against the effects of solar weather.

We're already building systems and technologies that are resilient.

But it would be even better if we could prepare for specific storms.

But for that, we need to know when they're going to arrive,

we need an early warning system,

and fortunately, there's one in this building right here.

Forecast's now trending downward.

There were several filaments that either erupted...

The Space Weather Prediction Center in Colorado

is the only team on the planet

solely dedicated to watching for solar storms.

No alerts or warnings are currently issued...

The aim is to alert governments, power companies

and the aviation and space industries that a storm is on its way.

Even a few hours' warning can help them prepare.

Chief forecaster Bob Rutledge

is going to teach me how to predict solar storms.

Space weather really starts with sunspots.

What that sunspot is doing, how much is it changing,

and how complex are those magnetic fields underneath those spots

are really what we use

to say how likely are we to have significant activity.

So what are the different events that could happen?

So when we get a solar flare, it's essentially the start of the event.

That's the giant explosion.

We see that, essentially, in this image in X-ray,

so it's a brightening in light and radio waves,

so that's our first clue.

The last piece is, does the portion of the sun's outer atmosphere

that sits above that, you know, a billion tonnes of plasma,

does it get blown into space as well?

So we start to watch other images of the sun,

like this, for example, where we've blocked out the centre.

We watch for the faint pieces of atmosphere being blown into space.

So the ones that go off to the side, albeit beautiful,

-don't really matter to Earth.

-Right.

It's really looking and seeing if it's coming our way or not,

and if so, how fast, and when do we expect it to get here?

These images are coming from the same new generation of satellites

used by the scientists at RAL.

They're our eyes in space that keep watch over the sun.

I can see it with visible light.

Magnetic fields.

X-rays.

On a typical day near solar maximum,

the sun will send out three coronal mass ejections.

Fortunately, today there haven't been any.

But dramatic events can happen with little warning.

You've got a video here of a very special event.

I've picked out from late October 2003

probably the last significant,

really big round of space weather activity that we had.

We've blocked out the sun so we can see the atmosphere.

You'll see the eruption.

-Oh, yeah! Really symmetrical.

-Look at that. Massive cloud.

It looks like a halo, coming straight at you.

It was going at tremendous speed, so it made it here in under a day.

So we have levels one through five, just like a hurricane or tornado,

-and it was pegged at that five level storm.

-It was as big as it gets.

That solar storm took out the power grid in the Swedish city of Malmo.

Tens of thousands were left without electricity.

On that occasion, the Earth was only struck a glancing blow,

but we can't be sure that next time we'll be so lucky.

Today, if we saw this happen again,

we'd be able to give our partners in the key industries,

like the electric-power industry, a heads-up to say,

"Hey, prepare your systems, keep them as safe as you can."

We're only just beginning to understand solar weather,

but we can't afford to ignore it.

I've been looking at the sun all day

and yet I haven't actually seen very much sunlight, and now it's got dark.

But here's what gets me about today.

Imagine the big weather events we have on Earth,

you know, thunderstorms and even bigger than that, hurricanes.

And then take a step back,

and all those massive events suddenly become tiny specks on the Earth,

sailing through this solar weather, which is even bigger.

We've come a long way

from the idea of the sun as simply a giver of light and warmth.

Its effects on our planet are far more complex.

Thanks to solar scientists, our sun is being revealed

as a dynamic, vigorous fusion reactor,

pulsing through its 11-year cycle

and belching plumes of highly charged particles in our direction.

As the scientists at RAL have shown us,

that 11-year solar cycle

has become the heart of how we understand the sun.

Many of the more surprising effects the sun has on our lives

depend on how its activity rises and falls through the cycle.

But scientists are now beginning to explore a radically new idea,

that these cycles are not as set as we once thought.

The latest research suggests that the cycles themselves could be changing.

We could be living through bigger shifts in the sun's behaviour

than we thought.

The clue comes from a phenomenon

that astronomers have been observing for centuries -

sunspots.

They've been known about since long before the era of satellites,

or even telescopes.

Looking directly at the sun without proper filters

is clearly a terrible idea,

because you could really, really damage your eyes.

But that didn't stop early astronomers from trying.

And just sometimes, maybe at sunrise or sunset or on a cloudy day,

they'd see something that made the sun worth looking at -

tiny dark spots.

And for years, they just assumed that those spots

were planets that were passing between the Earth and the sun.

And then the telescope was invented,

and Galileo could draw diagrams like these

and map out where these dark spots were.

And it became apparent

that they're actually part of the surface of the sun.

Thanks to those early astronomers,

sunspots are one of the few bits of evidence we have

about the sun's long-term behaviour.

And new research is revealing something surprising about them.

The key is how they're created.

Sunspots are caused by the magnetic fields deep inside the sun,

and we can't see those magnetic fields directly,

but the sunspots are offering us some clues as to what's going on.

And we know that the more active the sun is, the more sunspots there are.

As the sun approaches solar maximum

and the magnetic field lines beneath its surface become tangled,

the flow of plasma within is disrupted.

Hot material from the interior can't rise to the surface.

The result is zones of cooler plasma.

Sunspots.

They're like windows in the sun's surface,

through which we can study what's happening inside the sun itself.

The McMath solar telescope in Arizona is the largest in the world.

17 years ago, a study of sunspots began here,

led by a group of astronomers, including Matt Penn.

'They began to look at the average strength

'of the magnetic fields in the sunspots.'

So here we have the main mirror...

'Something no-one had tried before.'

So what got you started on this study?

So we wanted to take regular observations of the sun

to find out what sunspots were doing over time.

We know that the number of sunspots

increases and decreases in the solar cycle.

Actually, that's how the solar cycle was discovered,

by early observations of sunspots.

During solar minimum, there'd be zero or five sunspots on the disc.

During maximum, there could be 100.

During that 11-year period,

we wondered what was happening to the magnetic fields in sunspots.

Was it increasing along with the number of sunspots?

Was it flat, or was it doing something else? We just didn't know.

-And is it what you'd expect?

-Well, no, it turns out

that the data showed us something completely different.

Matt and colleagues are using an ingenious way of measuring

the strength of the magnetic field and sunspots.

A change in the infrared light coming from them.

So this is a really lovely, simple method,

because you can point your telescope at any point on the sun

and from the light coming out of it,

this simple thing of watching how these spectral shapes change,

you can see exactly how strong the magnetic field is

anywhere on the face of the sun.

Exactly, so we measure the magnetic field with the spectral line,

and we've done a survey of 3,000 sunspots over the past ten years,

measuring the magnetic field strength in each sunspot.

And what they've discovered is surprising.

Instead of rising and falling

in line with the solar cycle, as expected,

the magnetic strength of sunspots

has been steadily decreasing year by year.

Right back in 2000, the magnetic field was quite high,

and it's just gradually gone down and down and down

over the past ten years, quite consistently.

So a decreasing trend means that in the future,

we may not have any sunspots at all.

It's an extraordinary result.

The trend suggests

that, over and above the familiar 11-year solar cycle,

there are bigger patterns in the sun's activity.

And in the long-term, we may be heading for an extended quiet period,

what solar scientists call a grand minimum.

Intriguingly, we've been here before.

Thanks to those historical records, we know that around 350 years ago,

sunspots almost vanished for 70 years.

So it looks as though the sunspots could be dying away.

If that happens, what difference does that make to us?

Right, if sunspots do go away and we enter a new grand minimum,

there are possible effects on the climate.

Records suggest the temperature in Europe, for instance,

decreased during the last grand minimum.

A grand minimum would be a double-edged sword.

It might mean fewer solar storms, something in our favour.

But it could also mean a dramatic change in our weather.

The previous grand minimum

coincided with a period of brutally harsh winters

in Europe and North America.

The River Thames in London famously froze solid.

It was known as the Little Ice Age.

So this is a sort of intriguing time, right?

You can see maybe just the start of these big changes,

but you can't quite see why they're happening.

-But there are potentially very big impacts if they do.

-Exactly.

This data suggests that the sun is going through a major change,

a global change on the sun.

So in the long-term life of the sun, we'd love to know what's going on.

If this trend does continue,

it may be evidence of a bigger cycle in the sun's behaviour

that we've only just begun to glimpse.

But the sun works on such vast timescales,

even several hundred years of data can give us only a tantalising clue.

So we've been watching the sun for a few centuries,

but we don't know what was happening when the pyramids were being built,

or when the dinosaurs were alive, or a billion years ago.

And we don't know what's going to be happening

a billion years into the future,

so we're just seeing this tiny, tiny sliver of the lifetime of the sun,

and it's really hard to imagine that in this enormous timescale.

And that's the big challenge that lies ahead for solar scientists.

What's emerging is that even the pattern we thought we knew,

the 11-year solar cycle, isn't the full story.

There are bigger, longer-term patterns in the life of our sun,

and they could have profound influences on our planet and others.

What's incredibly exciting

is just how quickly our knowledge of the sun is growing.

And thanks to huge technological and scientific advances,

its surprises are gradually being uncovered.

And next time you feel the sun warm your cheeks

or you admire a sunrise, it's worth remembering

just how complex and wonderful our local star really is.

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