Are the Northern Lights dangerous? - Fabio Pacucci
On September 1st, 1859, miners following
the Colorado gold rush woke up
to another sunny day.
Or so they thought.
To their surprise,
they soon discovered it was actually 1 am;
and the sky wasn’t lit by the Sun,
but rather by brilliant drapes of light.
The blazing glow could be seen as far
as the Caribbean,
leading people in many regions to believe
that nearby cities had caught fire.
But the true cause of what would come
to be known as the Carrington Event
was a solar storm—
the largest in recorded history.
Solar storms are one of many astrophysical
phenomena caused by magnetic fields.
These fields are generated by movements
of electrically charged particles
like protons and electrons.
For example, Earth’s magnetic field
is generated by charged molten metals
circulating in the planet's outer core.
Similarly, the Sun’s magnetic field
is generated by large convective movements
in the plasma that composes the star.
As this plasma slowly swirls,
it creates areas of intense magnetic
activity called sunspots.
The magnetic fields that form
near these regions
often become twisted and strained.
And when they’re stretched too far,
they snap into simpler configurations,
releasing energy that launches plasma
from the Sun’s surface.
These explosions are known
as coronal mass ejections.
The plasma— mostly made of protons
and electrons— accelerates rapidly,
quickly reaching thousands
of kilometers per second.
A typical coronal mass ejection covers
the distance between the Sun and the Earth
in just a couple of days,
flowing along the magnetic field
that permeates the solar system.
And those that cross the Earth’s path
are drawn to its magnetic field lines,
falling into the atmosphere
around the planet’s magnetic poles.
This tidal wave of high-energy particles
excites atmospheric atoms
such as oxygen and nitrogen,
causing them to rapidly shed
photons at various energy levels.
The result is a magnificent light show
we know as the auroras.
And while this phenomenon is usually
only visible near the Earth’s poles,
strong solar storms can bring in
enough high energy particles
to light up large stretches of the sky.
The magnetic fields in our solar system
are nothing
compared to those found in deep space.
Some neutron stars generate fields
100 billion times stronger
than those found in sunspots.
And the magnetic fields
around supermassive black holes
expel jets of gas that extend
for thousands of light years.
However, on Earth, even weak solar storms
can be surprisingly dangerous.
While the storms that reach us
are generally harmless to humans,
the high-energy particles
falling into the atmosphere
create secondary magnetic fields,
which in turn generate rogue currents
that short-circuit electrical equipment.
During the Carrington Event,
the only widespread electrical
technology was the telegraph.
But since then, we've only become more
dependent on electrical systems.
In 1921, another powerful solar
storm caused telephones
and telegraph equipment
around the globe to combust.
In New York, the entire railway system
was shut down and fires broke out
in the central control building.
Comparatively weak storms in 1989 and 2003
turned off regions
of the Canadian power grid
and damaged multiple satellites.
If we were hit by a storm as strong
as the Carrington Event today,
it could devastate our interconnected,
electrified planet.
Fortunately, we're not defenseless.
After centuries of observing sunspots,
researchers have learned
the Sun’s usual magnetic activity
follows an 11-year cycle,
giving us a window into when solar storms
are most likely to occur.
And as our ability to forecast
space weather has improved,
so have our mitigation measures.
Power grids can be shut off
in advance of a solar storm,
while capacitors can be installed
to absorb the sudden influx of energy.
Many modern satellites and spacecraft
are equipped with special shielding
to absorb the impact of a solar storm.
But even with these safeguards,
it’s hard to say how our technology
will fare during the next major event.
It’s possible we’ll be left with only
the aurora overhead
to light the path forward.
