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When the sun erupts

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The sun is susceptible to a number of different eruptions — including solar flares — that spew particles into space.

Solar eruptions can be beautiful, but they are also highly unpredictable. And they can affect our daily lives in ways most people don’t realize.

Sunspots: An early warning

One such eruption starts with sunspots, which are cooler regions on the sun’s surface.

Like Earth, the sun is essentially a magnet with north and south poles.

MagnetMagnet with magnetic field circulating from north to south poleNS

But the sun is not a solid mass, so different parts of it rotate at different speeds. As a result, the sun’s magnetic field lines can become entangled, and sometimes, these sunspots release a sudden explosion of energy called a solar flare.

SunOur sun’s rotating magnetic field distorts over time and can develop loops where solar material is ejected

Often, a solar flare is followed by huge bursts of charged particles, called a coronal mass ejection (CME). These charged particles move incredibly fast — sometimes more than 3,000 kilometres per second — on what astronomers refer to as the solar wind.

Another way particles can be expelled is through coronal holes. These regions on the sun’s surface are cooler and less dense than the surrounding areas. As in the case of sunspots, the sun’s magnetic lines provide an opening where the solar wind is able to escape more easily into space.

Earth’s magnetic field

When a wave of these particles travels toward Earth, it disrupts our magnetic field. Earth’s magnetic field is pushed backward until it snaps, and charged particles are funneled toward the poles.

MagnetosphereThe field of Earth’s magnetosphere bends and snaps when charged particles from a solar flare collide. Charged particles then funnel back toward the poles where they become visible as auroras.

Lights in the sky

When charged particles from the sun collide with molecules in our atmosphere, they excite the electrons of those molecules. When the electrons return to their original charge, they emit visible light.

The colour of that light depends on the kind of molecule and the altitude of the collision.

Atmosphere interacts with charged particlesCharged particles collide with atoms in our atmosphere, causing them to emit different colours of light.100 km300 kmOxygenOxygenNitrogenNitrogen

Green is the most common colour, produced when the particles collide with oxygen at an altitude of around 100 to 300 km. At about 300 to 400 km, the interaction with oxygen produces red. Pink occurs below 100 km when nitrogen atoms are struck.

All these individual interactions combine to make waves or curtain effects along magnetic field lines.

This activity can result in a dazzling spectacle, but waves of charged particles can also disrupt satellites and power grids.

The Carrington Event

At 11:18 a.m. on Sept. 1, 1859, English astronomers Richard Carrington and Richard Hodgson independently recorded the earliest observations of a solar flare on the surface of the sun.

Carrington sketched what he saw.

Points A and B mark the position Richard Carrington saw the flare emerge. C and D indicate where it moved before disappearing (Richard Carrington/American Scientist)Hours later, a geomagnetic storm hit Earth.

Like lightning, charged particles always take the path of least resistance. When the Carrington coronal mass ejection reached our planet, that path was telegraph wires. Telegraphs all over Europe and North America failed; in some cases, they burst into flames. Telegraph operators received electric shocks.

In some cases, their machines mysteriously continued to work, even after they disconnected the batteries. In a way, the telegraph machines were temporarily solar-powered.

Blackout in Quebec

Today, electronic networks are interwoven with almost every aspect of our lives.

If a solar storm as powerful as the Carrington Event comes, it will affect everything we’ve come to depend on in our daily lives, such as our cellphones, GPS and electricity.

We’ve actually seen what it can do here in Canada. On March 9, 1989, a coronal mass ejection struck Earth. The particles travelled along the Canadian Shield and eventually found a weakness in the long transmission lines of Hydro-Québec’s power grid. Breakers tripped all over the province. The power failure lasted nine hours.

Solar eruptions are a wondrous, in many ways still mysterious phenomenon, which is why scientists are working hard to understand them.

MontrealCity of Montreal under blackout conditionsmontreal_master_v01

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