(thunder rumbling)
...a team of scientists takes to the air
to investigate a mystery.
I reported it, and nobody believed me.
(laughs)
NARRATOR: They're trying to catch a burst of energy
so fleeting and hard to see
that scientists call it by the ethereal name of "sprite."
EARLE WILLIAMS: The bolts that cause sprites are super-bolts,
the kind of lightning that'll blow your TV sky high.
NARRATOR: Unlike the brilliant Northern Lights,
created in the upper atmosphere
by streams of charged solar particles,
sprites are high-altitude sparks
that originate right here on Earth.
They're leading researchers on a chase
into the far reaches of the upper atmosphere
to a little-explored region,
home to many mysterious phenomena.
You can see airglow, that's more diffuse
and just in layers than the curtain-like aurora.
NARRATOR: NOVA takes to the air
on a quest to record these elusive events.
Sprite!
NARRATOR: And the effort also continues above
from the vantage point of space, where the work had its beginning
during the ill-fated Columbia mission,
with Israeli astronaut Ilan Ramon.
I asked him, "Please bring me one sprite image."
He said, "Don't worry, I'll get you a couple."
NARRATOR: Ramon's colleagues now continue where he left off.
SATOSHI FURUKAWA (translated): We must take over their work.
I thought that was the survivors' duty.
NARRATOR: Their dramatic discoveries
are revealing that we live on an electrified planet,
surrounded by a global circuit that rings the Earth.
And like a planetary heartbeat, we can now detect it.
It is like taking the EKG of the planet.
NARRATOR: High above the air we breathe,
at the boundary of a new frontier,
journey with us to the edge of space,
right now on NOVA.
Major funding for NOVA is provided by the following:
The Boeing Company.
The Corporation for Public Broadcasting.
And by contributions to your PBS station from:
Additional funding from:
In the darkness of space
there are violent forces at work.
Cosmic rays shoot across the universe,
asteroids billions of years old stream towards Earth,
and solar winds wreak havoc.
Their destination: the edge of space.
Our upper atmosphere:
it's Earth's first line of defense
against the hurtling space rocks
that we see flare into brilliance as meteors;
a protective buffer against the high-energy solar wind
that creates the beautiful Northern Lights;
and crucially, it is a key link in a global electric circuit
that blankets the planet from pole to pole.
Far below, the surface of the Earth
is hammered by eight million bolts of lightning every day:
up to 100 strikes every second.
Most lightning strikes from the clouds
towards the surface of the Earth.
But occasionally, the most powerful bolts
are accompanied by a ghostly and fleeting flash above the clouds,
reaching all the way to the very edge of space,
but lasting only milliseconds.
It's been a decades-long challenge
to understand these mysterious bursts of light.
Now, from the high vantage of the International Space Station,
it may finally be possible to capture images
of these rarely seen events
in the boundary between Earth and space.
But what defines this region?
Earth's atmosphere is a thin blanket of gas.
The troposphere is the lowest and densest layer.
All of life as we know it depends on this relatively thin,
five- to ten-mile-thick band of protective air.
Its thickness varies with latitude and the seasons.
This is where most weather occurs,
including the towering thunderclouds
that generate lightning.
A high-altitude helium-filled balloon
ascends quickly through this region
and enters the stratosphere, where most jet planes fly
and where the ozone layer is found,
which absorbs the Sun's ultraviolet light
that can damage living things.
Moving into this hostile environment,
the air pressure drops, causing the balloon to expand.
Up here, the lack of oxygen would quickly kill a person.
The stratosphere reaches an altitude of about 30 miles.
Eventually, the balloon cannot rise any higher,
but the ever-thinning upper atmosphere,
including the ionosphere,
extends another 500 to 600 miles,
even beyond the orbital height
of the International Space Station,
which circles Earth
at an altitude of between 200 and 270 miles.
From here, the ISS looks down on the planet.
At this altitude,
the environment is instantly lethal.
The extremely low pressure
would cause a person's body fluids to vaporize in seconds,
while the little air that remains can reach temperatures
of more than 2,000 degrees Fahrenheit.
There are also dangers of radiation exposure
in this forbidding atmosphere.
But safely aboard the ISS,
an international team of astronauts lives and works,
including, on this mission, Satoshi Furukawa,
a native of Yokohama, Japan.
An ardent baseball fan,
he takes advantage of zero gravity to play a solo game.
A medical doctor, one of Furukawa's jobs on the station
is to study the effects of micro gravity
on the human body.
He often conducts research as both doctor and patient.
He is also the mission photographer.
Using an extremely sensitive high-definition camera,
Furukawa will capture nighttime images
of Earth's upper atmosphere.
The ISS is an ideal platform to study the edge of space,
thanks to the Cupola observation window.
It offers a priceless view of space and the planet below.
Its heavy shutters open to reveal windows
for photography and viewing.
It's from here that Furukawa will aim his camera
when the station's orbit takes it into the Earth's shadow,
which it passes into about every 90 minutes
as it orbits the planet.
Designed to capture never-before-seen phenomena,
it is so sensitive that it can shoot color images
in near total darkness, bringing to light
places once hidden by the blackness of space.
He's hoping to capture images
of an elusive and mysterious form of high-altitude lightning
only recently discovered and still little understood.
The story of these strange lights in the sky
began one night in 1973,
when a U.S. Air Force pilot named Ronald Williams
was surprised by an unusual sight.
There was a typhoon over the South China Sea.
I happened to be flying over the typhoon.
And as I was going right towards the center of the typhoon,
there was a big thunderstorm,
just off the center of the typhoon.
All of a sudden, just by accident,
I was watching it because
if I had been doing anything else, I wouldn't have seen it.
NARRATOR: Williams saw a bolt of lightning
go straight up from the top of the clouds.
When it came up, I happened to be watching it,
and I just watched it go up.
I reported it, and nobody believed me.
(laughs)
They said, "Lightning don't go straight up.
It has to discharge on something."
NARRATOR: But it turned out that Williams was not the only pilot
to see lightning emerge from the top of a cloud
and shoot upward towards space.
As sightings accumulated,
they became a part of aviation folklore--
rare and unconfirmed events
that hovered just outside the boundaries of real science--
until another chance sighting provided more evidence.
EARLE WILLIAMS: A fellow by the name of Jack Winckler
had some detectors out.
He was looking for something else,
but he discovered them by accident
with equipment that was operated on dark nights in Minnesota.
NARRATOR: While testing a low-light video camera in 1989,
Jack Winckler and a team at the University of Minnesota
accidentally captured a black and white image
that seemed to show the elusive "upward lightning"
the pilots had described.
Fittingly, this ethereal phenomenon
became known as a "sprite,"
a whimsical name that captures its fleeting nature.
These giant pillars of light
sparked an intensified interest in lightning
and the dangers it presents to spacecraft
during launch or landing.
Today, astronaut Satoshi Furukawa
is looking for thunderstorms.
Sprites are only found where lightning is present.
But spotting sprites isn't easy:
they only accompany bolts of lightning
over ten times more powerful than normal lightning.
In ten minutes, it will be nightfall again,
so Furukawa quickly prepares his camera.
FURUKAWA: Recorder power is on.
Monitor is on, too.
NARRATOR: This specialized camera
should be able to capture images of the elusive sprites,
even in these low-light conditions.
He'll need this extra sensitivity
to catch a sprite.
If any sprites appear,
they will be above powerful bursts of lightning.
Across the world,
over 2,000 lightning bolts flash every minute,
and over 20 million strike the U.S. each year.
They're four to five times hotter
than the surface of the Sun, and the most potent
can discharge up to a billion volts of electricity.
Unlike the superheated lightning flashing below the storm clouds,
the sprites above are huge but electrically much weaker--
and faster, disappearing on average
in less than 70 milliseconds.
Furukawa maintains his vigil for several hours,
but without much luck.
FURUKAWA: Hmm, it's difficult...
NARRATOR: His camera recorded a huge number of lightning flashes,
but no sprites appeared above them.
FURUKAWA: I felt like a hunter.
It was impossible to predict where it would appear.
NARRATOR: Though the search is frustrating and difficult,
he is determined to capture a sprite,
in part because of a letter he received
during training for his ISS flight.
The letter was from an Israeli lightning expert, Yoav Yair,
who wrote to inquire about the mission.
He enclosed a photo of Ilan Ramon,
Israel's first astronaut
and a crewmember of the ill-fated Columbia mission.
Ramon had brought with him
a high-sensitivity black and white camera
to try to capture images of sprites from space.
RAMON (recording): It's a big day for the Israeli science community.
NARRATOR: Ramon's partner in the research was Professor Yoav Yair.
I asked him, "Please bring me one sprite image."
He said, "Don't worry, I'll get you a couple!"
NARRATOR: After capturing over nine hours
of thunderstorm footage on board,
he succeeded,
and transmitted several images of sprites back down to Earth.
But tragically, Columbia never made it home.
It disintegrated upon re-entry.
Though debris was scattered widely,
the camera that Ramon had used to capture sprite images
somehow survived,
with some of Ramon's work intact.
One image of active lightning over Central Africa
shows a bright flash of light above the lightning
and arcing up towards space.
It was a sprite.
Ramon captured images like this one
from several vantage points in orbit.
Yair and his research team studied these photos
and were surprised to discover
how frequently sprite events occurred
over large tropical storms,
and how widely distributed they were.
But there was still much to learn.
Yair saw Furukawa's mission as a great opportunity
to advance the understanding of sprites.
FURUKAWA (translated): It's so touching.
I can feel their passion.
I was there at their scheduled landing spot
and looking up at the sky.
The Columbia never came back.
They were my friends and my colleagues.
I was very sad to lose them.
At first, it was difficult to get back on track.
I didn't feel like doing anything.
Then I thought,
"We must take over their work and move forward."
I thought that was the survivors' duty.
So I am honored and happy
that I was given this chance in this way.
NARRATOR: So nearly 250 miles above Earth,
Furukawa is working hard to further Ramon's legacy.
He readies his camera
as the flight path takes him towards Europe
and into the nighttime darkness: Earth's shadow.
He won't have much time.
At ISS speeds,
traveling over Paris to Rome takes just two minutes.
Looking down, he sees the lights
rimming the boot-shaped peninsula of Italy.
In ten minutes, he'll be over Central Africa.
Weather patterns and topography
make this the world's most lightning-prone region.
Because it's estimated that
only one in 10,000 lightning bolts produces a sprite,
Africa's very active skies make it one of the best places
to spot one of these elusive events.
So the first step in capturing a sprite is to track
the kind of extraordinary, monster thunderstorms
that produce super-bolts of lightning.
And figuring out where they might be is Yoav Yair's job.
He analyzes weather patterns on the ground
and sends the locations
of potential sprite-producing thunderclouds
to Furukawa on the Space Station.
This is a very exciting and emotional thing for me to do
because it reminds me of the things we did
for Ilan Ramon and the crew of the Columbia in 2003.
NARRATOR: With Yair guiding him, Furukawa circles the globe
looking for the kind of monster thunderclouds
that could produce a sprite!
Then, while flying over the Middle East...
FURUKAWA: Incredible!
NARRATOR: ...he sees something.
It's clearly a sprite flashing over the thundercloud
and surging towards space.
And it looks like a color version of the one captured
by Ilan Ramon from the Columbia space shuttle.
It's the first clear high-definition color photograph
of a sprite taken from above.
And there are more.
Ahead is Taiwan, Japan and mainland China.
A giant sprite appears over Beijing, near the horizon.
The white flash below
is an unusually powerful bolt of lightning.
The sprite above is far off.
It may not look especially large,
but some sprites can be almost 40 miles in height:
dozens of times taller than ground-striking lightning bolts.
Altogether, Furukawa captured six sprites.
FURUKAWA: It was a real surprise to me.
It's so exciting when something previously invisible to us
finally starts to become visible.
NARRATOR: The footage was sent to Yoav Yair
and an international team of sprite researchers
who are continuing the work of Ilan Ramon
and the lost Columbia crew.
Oh, very nice!
Now it's much more detailed, better camera, color--
we only had black and white--
but it was really exciting for me.
Actually, it really moved my heart to see it.
I have to imagine this
because they are not with us-- they're all gone--
but I am sure that if he knew
that their mission was accomplished eight years later
or maybe even going on later, they would feel fulfilled.
He would be proud, I think.
NARRATOR: Images like these are helping scientists to understand
how a huge storm can generate sprites.
During a thunderstorm,
electric charge builds up in a thundercloud,
causing lightning to emerge from the lower part of the cloud
and strike the Earth,
discharging an immense electric current.
But if that lightning bolt is powerful enough,
it can trigger a sympathetic spark above the cloud.
EARLE WILLIAMS: As you go up in altitude, the density of air decreases.
And so low-density air is easier to make a spark in
than high-density air.
So a Sprite is really caused by lightning
down in the lower atmosphere
that exerts a stress on the upper, thinner atmosphere
and causes a spark up there.
NARRATOR: And that spark gives rise to a sprite.
As the scientists examine the images,
there's one that attracts a lot of attention.
Captured in one of Furukawa's pictures,
the top of one of the sprites
seems to reach all the way to the airglow layer.
The airglow is part of the ionosphere,
which is a vast sea of electrically charged particles,
or ions.
It's these particles,
with help from the Sun, that create the glow.
Airglow is due to solar radiation at short wavelengths--
ultraviolet wavelengths, UV, the same stuff that sunburns us
if we're outside without our sunblock--
or X-rays, you know, that we use to image our bones.
And that can transfer energy
to the molecules in the atmosphere,
and that energy transfer causes a glow.
NARRATOR: But the most important thing about the airglow
may not be why it glows, but where it's located.
It's the lowest part of the ionosphere,
the uppermost region of the atmosphere.
It begins about 60 miles above Earth
and extends over 600 miles to the very edge of space.
The airglow is just the most visible component
of the ionosphere,
which is created by radiation from the Sun
interacting with the topmost layer of Earth's atmosphere.
So the image of a sprite reaching the airglow
shows the incredible heights these massive sparks can reach.
But these stunning images from the Space Station
still leave many questions unanswered.
How exactly do sprites form?
And what accounts for their peculiar shape?
To answer these questions,
the group decides to try something
that's never been done: to fly closer to sprites
and to photograph them simultaneously
with two different cameras on two different airplanes,
hoping to combine these images digitally
and reveal the anatomy of a sprite.
The planes will also be equipped
with the same super-sensitive color HD camera
Furukawa has been using on the International Space Station.
But their real secret weapon
is a high-speed black and white camera
that shoots 10,000 frames per second
under low-light conditions.
It will be able to show the formation of sprites
in slow motion.
It will be the first time that we have had two aircraft
simultaneously trying to image a sprite
with high-speed cameras.
Sp it's very exciting for us.
NARRATOR: They chose the area
where the Great Plains meet the Rocky Mountains
as a likely place to hunt for sprites
because it is famous for very big nighttime thunderstorms.
You can see huge thunderclouds there in the summertime.
The weather is sunny almost 70% of the year.
The intense sunlight heats the ground
and causes a strong upward air current.
This, in turn, creates active thunderclouds one after another,
producing lightning.
But only the biggest lightning flashes of all produce sprites.
And once again, it will be Yoav Yair's job
to help the team in the air
find those huge sprite-producing thunderclouds.
He and his team will be at the Yucca Ridge Field Station,
a weather observation facility
on the Great Plains north of Denver.
Oh, you got it.
No, no...
You got it okay.
NARRATOR: They will forecast where a sprite might appear
and direct the planes.
At 5:00 p.m., the flight team gathers
to discuss strategy for tonight's mission.
They call the control station.
Scientist Geoff McHarg, who will be on one of the planes,
is asking for the lightning forecast.
We were just looking at the charge moment change map
and then the weather map...
WALT LYONS: It's not weakening.
The good news is
it's moving into some extremely unstable air.
NARRATOR: Walt Lyons of the Yucca Ridge Field Station
is working with Yair to analyze the weather data.
In this satellite image, clouds are shown in blue.
That day, thunderclouds were developing
in a variety of places.
But would they produce powerful enough lightning
to produce sprites?
Back at the airport, the pilots talk among themselves.
Usually they avoid big storms,
but tonight they will have to fly in
and around the thunderclouds,
hunting for the perfect position to capture sprites.
They know it will be a rough and difficult flight.
(thunder rumbling)
As soon as it gets dark,
thunder begins to reverberate around the airport.
The researchers board the planes
on what looks like a promising night.
At 9:00 p.m., the two jets take off.
They're heading for thunderclouds 120 miles away
that are vigorously producing lightning.
The cabin is in constant communication
with Yair and Lyons at Yucca Ridge.
Essentially, they want some kind of central location.
NARRATOR: He evaluates the data and gives the pilots
the latitude and longitude of large thunderclouds
where sprites might appear.
We'll be on this data collection run
for about ten minutes.
NARRATOR: Outside the window,
they see a huge thundercloud begin to glow with lightning.
MAN: It's here!
Lightning!
Quite promising.
NARRATOR: Somewhere in the darkness above the cloud,
they are hoping a sprite will occur.
The high-speed camera is adjusted slightly upwards
to shoot the area above the flashing thunderclouds.
Geoff McHarg, who has spent 20 years chasing sprites,
can barely contain his excitement.
But Yair and Walt Lyons on the ground
can see an unexpected change in the thundercloud.
YAIR: They are here,
and if they go like this, they would get this part, but...
LYONS: You know, both of them are starting to weaken.
NARRATOR: The large thundercloud that was expected to grow
has started to split in two.
They've been in the air for five hours
with no sign of those elusive sprites,
and now the lightning is quickly losing momentum.
Despite the promising forecast and their careful preparation,
they have no choice but to return to the airport defeated.
It was horrible.
MAN: Until we got high.
Yeah.
I've seen much larger storms, you know,
where you get really large sprites
that happen pretty often, and this was just too small.
We'll see.
Fingers crossed for the next one.
NARRATOR: They realize this will not be easy.
On the Fourth of July,
while people all over America are celebrating,
the sprite team hurries to the airport.
They've been waiting
for the right kind of weather for a week.
Finally, new storm clouds
powerful enough to generate sprites have appeared.
McHARG: So if we go here...
If we don't see lots of sprites
and this starts to get more intense,
then I may want to extend up.
Go as soon as they get ready, I would say.
NARRATOR: Both planes take off into a stormy sky.
While Denver watches fireworks below,
they prep the cameras and get ready.
30 seconds.
NARRATOR: They start to see flashes of lightning below.
On the ground, Yair and Lyons are trying to figure out
the best way to position the planes.
But then they would have to turn down,
or do you want them to circumvent it?
Well, can they punch through and come around the other...
Go all the way and...
Up to about 47 degrees
and see if they can punch through.
NARRATOR: The two thunderclouds shown in deep blue have collided,
and major cloud development has begun.
They send the coordinates of the strongest lightning
to the team in the air.
NARRATOR: Outside, lightning flashes are everywhere.
A monster cloud, with a diameter of more than 300 miles,
is releasing electricity with frightening intensity.
The scientists rush to position their gear.
The frustration and anticipation of the previous week
is getting to them,
and tension in the cabin is high.
Sprite!
Wow!
That's a heck of a sprite there!
Did you get it?
NARRATOR: For an instant, a giant red flash appeared.
On replay, they can see beautiful shafts of light
thrusting upwards toward space:
the mysterious sprite in all its glory.
Then the sprites keep coming.
Sprite!
We got sprites!
NARRATOR: On board, the team reviews the stunning and unique images.
This sprite was shaped like a mangrove tree.
It's been captured in more detail
than any sprite until now.
Just like its name,
this sprite evokes a fairy with wings.
MAN: Jellyfish!
Yeah, a very big jellyfish!
It's pretty, very pretty!
NARRATOR: It indeed looks like a jellyfish with many tentacles.
Sprites of many different forms appear one after another.
Seen up close, they have a variety of shapes.
Eventually, a sprite appears that demands special attention.
(translated): This is spectacular!
NARRATOR: The umbrella-like top of this sprite
reaches an altitude of around 60 miles.
That's the altitude of the airglow layer
that appeared in Furukawa'fo
from the International Space Station.
The image confirms that sprites interact with the ionosphere.
Now it's time for the high-speed camera.
It's designed so that when a sprite is sighted
and the button is released,
the previous three seconds of footage will be saved.
Sprite!
(crew talking excitedly)
NARRATOR: This is the momentary flash of a sprite
taken by the super-sensitive camera,
and when shot by the high-speed camera, it looks like this.
In just a few hundredths of a second,
countless particles of light rain down.
This is the first time a sprite's formation
has ever been revealed in such detail.
(crew talking excitedly)
NARRATOR: During the night,
14 sprites were captured by the high-speed camera.
8,000, yes, very good.
(crew talking excitedly)
NARRATOR What else will the footage reveal.
With great expectations they return to the ground.
Not too bad, huh? >>>Great!
Thats amazing.
It was fabulous.
It was amazing.
I haven't seen anything like that ever.
NARRATOR: The long night is over,
but they know their work is just beginning.
Back in Denver, the team gathers to make some scientific sense
out of their spectacular sprite footage.
The halo above and the elf below,
and that's just because it's expanded out in front...
NARRATOR: At first glance, this sprite may seem to burst up
from the storm clouds towards space.
But when seen by the high-speed camera,
the movement looks completely different.
Bursts of light appear out of the center,
spreading both up and down.
In fact, when examined in slow motion,
it appears that sprite formation is more complicated
than early reports had indicated.
And what about this sprite shaped like angel's wings?
With this one, too,
bursts of light suddenly appear out of darkness.
They go down, and the next moment, up,
and then down again.
They change their direction as they unfold.
So what is really happening?
Within the sprite, electrons are colliding
with charged particles in the atmosphere,
creating a pathway for the electrons to travel.
Where they go depends on the concentration of electrons
and the composition of the atmosphere.
Sprites are beautiful and intriguing,
but do they actually have a role to play
in Earth's upper atmosphere?
Yukihiro Takahashi is investigating
the aftermath of a sprite.
Once the electrons cut open a path,
the atmosphere around it becomes highly electrified.
Following the sprite's path, a large electric current
continues to flow from the thundercloud to the ionosphere,
which shows up as the airglow in many sprite images.
(translated): The sprite flashes only for an instant,
but at the moment when it flashes,
a conductive path is created.
The electrified path doesn't disappear
when the flash ends, but stays there for a while.
The effects are thought to last several seconds to minutes.
NARRATOR: The result is a massive transfer of electric charge
in the space between the cloud and the ionosphere.
The team also successfully captured a sprite
from different angles, as they had originally planned,
using high-speed cameras placed on the two aircraft.
By combining the images from the two cameras,
the three-dimensional structure of the sprite becomes apparent.
A large number of electrons collide with the atmosphere,
creating brilliant bursts of light
and opening channels where the electrons can flow.
Each sprite channel can be hundreds of yards wide.
A sprite event is like a switch
that turns on an electric current in the space
between the Earth and the ionosphere.
In fact, our planet is surrounded by electric current,
from the surface to the edge of space.
Like lightning, sprites help to complete a global circuit,
allowing charge to flow continuously around the Earth.
But sprites reach much farther than lightning,
and unlike lightning,
sprites can transfer charge into the ionosphere
to the edge of space.
Not only that, but the bolts of lightning
that create the sprites are so powerful
that they literally reverberate around the world.
EARLE WILLIAMS: When a sprite occurs,
the parent lightning that causes the strike
radiates electromagnetic waves.
Those waves propagate in what we call the global circuit.
NARRATOR: Earle Williams of MIT studies sprites
from this remote laboratory in western Rhode Island.
Williams and his equipment are nearly off the grid out here,
but they're completely plugged into the biggest circuit of all:
the Global Electric Circuit.
WILLIAMS: We've been monitoring this phenomenon
for nearly two decades at this site,
trying to look for long-term trends.
NARRATOR: In fact, scientists have actually been measuring
the Global Electric Circuit
on this unusual site since the 1950s,
when the lab was set up by Williams' predecessor,
Charles Polk of the University of Rhode Island.
WILLIAMS: The antenna immediately behind me is Charles Polk's.
The more distant antenna is one that we constructed
when Polk's antenna was struck by lightning
and it blew the antenna into many separate fragments
all over the meadow we're sitting in right now.
NARRATOR: Williams got involved with early sprite research
by collaborating with Walt Lyons
of the Yucca Ridge Field Station.
Every time Walt saw a sprite in Colorado,
which is roughly 2,000 miles from here,
we would see a big disturbance here in Rhode Island.
NARRATOR: The antenna Williams is using
measures a very low frequency wave,
like a steady hum that resonates
between the Earth and the ionosphere.
WILLIAMS: When a sprite occurs,
the lightning that causes the sprite
sends waves in that thin cavity around the world
two or three times,
and it is exciting something called the Schumann resonances.
And the Schumann resonances is a manifestation
of what we call the AC Global Circuit.
NARRATOR: Earle's aunt was a prominent violin player,
so it's not too surprising
that he thinks of it in musical terms.
WILLIAMS: The vibration of a violin string
is very much like what happens with Schumann resonances.
We have a fixed string length,
and there's one wave on the string,
which has a fixed frequency, say the A note of 440 hertz.
For Schumann resonance, we have a fixed length,
but the length wraps itself around the world.
And for that fixed length and the speed of light,
we have a fixed frequency of eight cycles per second.
So they're both examples of resonances,
this one being a mechanical resonance,
that one being an electro-magnetic resonance,
but the same wave phenomenon applies.
NARRATOR: It's almost like the music of the spheres--
or of the Earth, at least.
WILLIAMS: No matter where you are on Earth,
if you have an antenna, a vertical antenna
like the one behind me,
you will see an oscillation on that antenna
at roughly eight cycles per second.
And that is maintained continuously
by all the lightning on the planet.
Every time there's a lightning flash,
a small fraction of the energy in that lightning flash
feeds into this global resonance.
NARRATOR: The Schumann resonance is present all the time.
It never dissipates
because there's always lightning someplace on Earth.
And when a sprite is produced by a super-bolt of lightning,
there is a spike in the Schumann resonance signal.
WILLIAMS: Every sprite lightning is a bell ringer
for the Schumann resonances.
One of these giant lightnings
will single-handedly excite the whole Schumann cavity
with electromagnetic waves.
And everyone on Earth who has a receiver
in the range of frequency of eight cycles per second
will detect a sprite event.
Here on the oscilloscope,
we have an example of the Schumann resonant signals.
You can see the characteristic
eight-cycle-per-second oscillation, continuously.
That's called the background Schumann resonances.
Occasionally, you'll see a big increase in the amplitudes.
Those events are the events that make the sprites.
These are the lightning flashes,
the very energetic lightning flashes
that create sprites in the thin upper atmosphere.
NARRATOR: Earle's science may be cutting edge,
adding to our understanding of planet Earth,
but his equipment is a little bit old school.
EARLE WILLIAMS: Because the Schumann resonances
oscillate at only eight cycles per second,
it is kind of a low-tech operation here.
I mean, we do digital recording of the signals, but it's...
You know, these are very low frequency signals
you can put on an oscilloscope, and you don't need
high-bandwidth equipment to record them.
But you have to be in a quiet place.
You can't do this in the middle of a city:
there's too much background noise.
And that's why we're out here in this very beautiful site
in the middle of nowhere.
NARRATOR: And super-powerful lightning produces not only sprites,
but other weird phenomena as well.
There are actually a whole zoo of creatures up there
that are caused by lightning.
There's something called an ELVE,
and it's like a pancake of light within the airglow layer,
and it's caused by the radiation field from lightning.
Then there is a halo, which is also a pancake shape
but at somewhat lower altitude.
And then there are blue jets and pixies
and a whole host of other optical phenomena
that occur in conjunction with lightning flashes.
NARRATOR: Since the Schumann resonance fluctuates slightly
depending upon factors such as the temperature of the Earth,
Williams thinks it's one important way
of measuring the health of the whole planet.
WILLIAMS: It's a natural setup for looking at the entire Earth.
You have one quantity which represents the entire planet,
and it's hard to dream up another such circumstance.
It is like taking the EKG of the planet.
NARRATOR: The global electric circuit surrounds everything on Earth
and connects us to the edge of space.
Sprites feed into the ionosphere from below.
But from above, the Sun also affects the ionosphere,
resulting in the vivid displays of the Aurora Borealis.
Auroras are light displays
caused by the collision of charged particles
streaming from the Sun into our atmosphere.
There are two types of auroras.
The discrete aurora like the Northern and Southern Lights
have well-defined boundaries
that can be seen with the naked eye,
and diffuse auroras that spread out over a wide area
and are less colorful.
93 million miles away, auroras are born
from a landscape of blistering temperatures
and violent eruptions.
From the surface of the Sun, huge volumes of solar material
in the form of charged particles are blasted into space.
A fleet of satellites monitors this solar activity.
Stereo A and Stereo B satellites are making 3D images of the Sun
and also tracking solar activity.
These eyes in the sky paint a detailed picture of the Sun
and the powerful forces erupting from its surface.
The constant stream of charged particles,
the solar wind, is so violent,
it would strip away the Earth's atmosphere
if it hit our planet directly.
CAHOY: The sun you can think of
as a really big angry hair dryer in a lot of ways:
it's constantly blowing hot, energetic wind
out in all directions,
not just directly towards the Earth,
but in all directions.
And this hot, energetic, fast-moving particle stream
hits straight on with the Earth.
NARRATOR: Earth's magnetic field blocks and deflects the solar wind,
protecting our planet from a full-on assault.
But there is a back door
that allows some of the charged particles from the solar wind
to reach us.
In the Earth's shadow,
there is a region in space where charged particles accumulate.
These particles, though drastically decreased in number,
sneak in through small gaps in Earth's magnetic defenses.
The charged particles dash toward Earth...
...and interact with the magnetic field,
which deflects and diverts them to the poles.
They rain down, forming luminous rings in the sky.
The beautiful, vibrant colors of the aurora
are visible evidence of the particles' interaction
with Earth's second line of defense: the atmosphere.
CAHOY: The aurora are different colors at different altitudes
depending on the gases in the atmosphere
that the particles are interacting with.
So it's red at higher altitudes, it's oxygen,
and then blue and green, oxygen and nitrogen,
as it gets denser into the atmosphere
where the gases get thicker.
And then for really, really strong interactions
of the particles, energetic particles
really penetrating deep into the atmosphere,
you may even see a pinkish purple color
down at the bottom, where there's more nitrogen.
NARRATOR: But sometimes, things can go wrong.
Really wrong.
Sometimes, the blast of charged particles can be so intense
that the auroral ring thickens and vibrates explosively.
CAHOY: There are these periodic events, these coronal mass ejections,
where the gas just is incredibly more intense
than it normally is.
And this charged particle cloud will come out,
spiral out towards the Earth,
and our magnetic field will respond.
NARRATOR: The Earth's magnetic field does a good job of protecting us.
The more beautiful the aurora,
the more intense the battle at the edge of space.
And even satellites high above Earth
can fall victim to the power of our Sun.
In 1989, during a period of intense solar turbulence,
induced electric currents caused by the aurora
shut down the entire power grid in Quebec, Canada,
in under two minutes.
The province's largest city, Montreal,
was crippled by power outages.
Human activity throughout the region
came to a halt for nine hours.
The more recent "Halloween storms" of 2003
caused hour-long power outages throughout Sweden
and impacted satellites and aircraft communications.
But the greatest solar storm on record took place in 1859.
It created auroras so powerful
they illuminated skies as far south as Hawaii and Panama,
while playing havoc with telegraph systems
around the planet.
A similar storm today could devastate power grids
and communication systems and cost billions to repair.
In today's wired world, no one is invulnerable.
CAHOY: Solar storms can affect
satellite communications in different ways.
Performance of your handheld radio, your GPS receiver,
your satellite television receiver,
your satellite radio receiver,
all of these things can be affected by space weather.
NARRATOR: We think of electricity as a modern invention,
but the electric Earth has always been with us,
surrounding our planet
and connecting us to the edge of space.
AsterThis:NOVAlprograms on a colis available on DVD.arth.
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Captioned by Media Access Group at WGBH access.wgbh.org