The Secret Life of the Sun Page #4

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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

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