The science behind the northern lights (aurora borealis)

We all know the aurora borealis are a
spectacular display happening above. But do you really know what causes it? What
is the aurora borealis? When we watch that dazzling display of light it’s
actually telling us a story. It’s a story that began on the sun,
travelled all the way to Earth, had a series of interactions in the magnetic
field and led to this beautiful display overhead. The aurora borealis are caused
by particles– electrons and protons– blasted out from the sun in all
directions and colliding with gases in the Earth’s atmosphere. Those particles
travel 150 million kilometres from the sun to reach Earth. That can take from
two to four days. That flow of particles is called the solar wind. A lot of
particles when they reach the magnetic field are deflected away into space but
some become trapped in the magnetic field. And what’s going on is that
there’s this little spark that occurs. This release of energy that we see in
the form of light. And so now imagine that overhead there are billions of
these tiny little sparks going on. And the sequence of light, these little flashes
of light, are what we see and call “aurora.” So if you’re living in northern Canada
or northern Scandinavia, northern Russia around the north magnetic pole
and you look up, what you’re seeing is this waterfall of particles that are
following a magnetic field line into Earth’s upper atmosphere. So why are they different colours? The Earth’s atmosphere is made up of nitrogen, oxygen and other
gases commonly known as air. The colours of the aurora depends on the gas
molecules that the particles are mixing with. So green, the most common colour of
aurora, is a charged particle mixing with oxygen. Blue is when they mix with the
nitrogen. Generally along the lower edge we see a really intense, very vibrant
purple colour. That’s an indication of that of particles interacting with
nitrogen. Astronomer and physicist Galileo actually coined the term aurora
borealis in 1619. It was after aurora the Roman goddess of
morning. He mistakenly thought that the auroras were due to sunlight reflecting
from the atmosphere, according to NASA. Though Indigenous northerners have oral
traditions about the lights that go back generations.
How high up are the auroras? Aurora are between 100 and 500
kilometres above the surface of the Earth. How high is that? The International
Space Station orbits the Earth at about 400 kilometers above the surface.
Astronauts on the space station often get a side view of the aurora. That’s
still cool too because the side view of an aurora can give you an unbelievable
show. It shows you… how tall an aurora can be. Saturn and Jupiter also
have beautiful auroras even more powerful than Earth. There is a lot of
mystery around the aurora though. Scientists are always looking at new
missions to better understand the relationship between the sun and the
Earth and forecasting auroras and space weather. Modern day technology like cell
phones also depend on that research since satellites can be affected by the
solar wind. So why are aurora more visible in the north. Well, most auroras occur
in a band called the auroral oval. That’s a huge ring of aurora above the Earth’s
north and south magnetic poles. The northern lights we see are just a small
section of the auroral oval. Places like Alaska, Greenland, Scandinavia and
northern Canada are the perfect zone because they’re close to the auroral
oval. If you’re at high latitudes anywhere on the planet,
chances are every single night there is auroral activity overhead. When there is
active space weather, it can push the auroral oval like an elastic band
further south. That’s when people right across Canada, and even the United States,
can see the aurora. And let’s not forget the southern lights. People living
near the South Pole can see the aurora borealis’ cousin: aurora australis. It’s
really, truly a scientific wonder. And there’s a lot that we still don’t know
about when it comes to the auroras. Some of the most experienced scientists say that
for every question that’s answered there are ten more that need to be answered.
It’s a beautiful way to watch the sun and the Earth and their magnetic
connection and it tells a beautiful scientific story.