The Secret Life of the Sun Page #5

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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.

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