What Causes the Northern Lights?

There are many misconceptions about what causes the Aurora Borealis when it really requires solar winds, magnetic fields and excited atmospheric gases.

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Episode Transcript

Speaker 1 (00:00):
I'm at, I'm no, I'm Ben, and we are stuff
they don't want you to know. Each week we cover
the latest and strangest in fringe science, government cover ups,
allegations of the paranormal, and more. New episodes come out
every Friday on iTunes, Spotify, Google Play, and anywhere else
you get your podcasts. Welcome to brain Stuff from How

(00:24):
Stuff Works. Hey, brain Stuff, this is Christian Sager. We've
all heard of the Northern lights, right, those beautiful manifestations
of colors that are in the sky. Well, they've inspired
many myths. In Viking legends. They were considered the by Frost,
the many colored bridge between Earth and Asgar, the home

(00:46):
of the gods, and in Finland they actually believe the
lights were a sign of the archangel Michael battling the
devil bills above. Scandinavians believed that they were reflections off
of the shields of the Valkyries. But despite being observed
for thousands of years, there are still many misconceptions about
what the Northern lights are. First of all, it's false

(01:08):
that their sunlight reflecting off of polar ice caps. It's
also false that their moonlight reflecting off of ice crystals
in the air. The Aurora borealis, as it was coined
by Galileo Galilei and means northern dawn or dawn of
the North in Latin, is also at the South pole,
known as the Aurora Australia's. In eighteen nineties six, their

(01:31):
real origin was discovered by Norwegian scientist Christian Burkeland. He
tested his theory in controlled experiments and here's the truth
of the matter. Solar winds stream away from the Sun
and flow around the Earth's magnetosphere. They're charged electrons interact
with elements in our atmosphere at points where the magneto

(01:55):
sphere is weakest, the North and the South poles. So
these solar winds the Sun's corona continuously amidst them a
stream of electrically charged particles. They stream away from the
Sun at speeds of one million miles per hour. They
reach Earth in forty hours from the Sun. Now, this

(02:16):
is forty times faster than a spacecraft needs to be
to escape Earth's gravity. It's pretty fast. Solar activity currently
follows an eleven years cycle, and longer cycles affect the Aurora,
and we've actually seen them increased Solar activity in the
last few centuries. When they get here, though, these solar
winds strike the magnetic force generated by the Earth's core.

(02:41):
Then they flow through this magneto sphere, a shield area
of charged electrical and magnetic fields. This shield is then
blown into a tear drop shape by the solar winds.
The magneto sphere protects Earth from dangerous solar and interstellar particles,
and most are directed away from Earth, but some are

(03:03):
trapped near the magnetic poles. The electrons from these solar
winds interact with elements in Earth's atmosphere somewhere between sixty
to two hundred miles up in the air. This is
ten times higher, by the way, than most airlines fly.
These electrons collide with oxygen and nitrogen, transferring energy into

(03:25):
these gases and making them excited. When they calm down,
they emit photons and small little bursts of energy form light.
The shifts and flow of this energy can reach twenty
million ampiers at fifty thousand volts. Compare that to your
circuit breaker at home disengaging over fifteen to thirty ampiers

(03:48):
at one volts. So it's a lot of energy. Now,
the color of the aurora depends on which element, whether
it's oxygen or nitrogen, that is struck, and at what
altitude it's struck at. Since it's dimmer than sunlight, the
aurora actually can't be seen during the day. But oxygen

(04:08):
emits either a greenish yellow light somewhere around up to
a hundred and fifty miles up in the air, or
a red light over a hundred and fifty miles up
in the air. Nitrogen, however, emits a blue light up
to sixty miles up in the air. If you blend
them all together, however, you can produce purples, pinks, and

(04:28):
white light. But one note. While some say they have
quote heard the Northern lights, the air where they're formed
is actually too thin to conduct sounds, so that's not possible.
It would be impossible for sound to travel from the
upper atmosphere to the ground. So you're probably asking yourself,
these sound pretty cool. Where do I get to see
the Northern lights? Where do they occur? Well, they center

(04:51):
around Earth's magnetic poles, not the geographic polls, and they're
in ring shaped spots called auroral oval. These are between
five hundred and fifteen hundred kilometers wide and expand during
geomagnetic storms. These roughly correspond to the Arctic and Antarctic
circles and can be seen from space, so the best

(05:14):
places to see them are Central Canada, Alaska, Greenland, northern Scandinavia,
and northern Russia. And yes, if you're asking, other planets
also have auroras. They've also been observed on Saturn, Jupiter,
and Urinus. Check out the brain stuff channel on YouTube,

(05:38):
and for more on this and thousands of other topics,
visit how stuff works dot com.