Science With A Bit Of Flare
Apart from providing us with the occasional cool photo to gawp over, solar flares have a massive effect on the Earth. They've even been blamed for global warming. But what exactly are they? Mia Kukathasan takes a look at the weird world of Coronal Mass Ejections.
On March 13, 1989 a sudden total power blackout hit Montreal, Quebec; millions of people were plunged into darkness. Auroral lights lit the night sky red, pink and yellow, and strange phenomena were reported across the city; bedroom lamps that still glowed after the power had gone out and car radios re-tuning themselves into local radio stations hundreds of miles away. Navigational systems and space satellites were in danger and telecommunications were disrupted by electrical surges, blowing out the transformers and causing cables to burst into flames.
The Sun had just sneezed out a Coronal Mass Ejection - think of it as an extra big solar flare - from over 90 million miles away. This massive burst, travelling at 8 million kilometres an hour is the biggest kind of explosion that occurs in the entire solar system. They occur, on average, between one and ten times a day; on March 13th 1989, one simply happened to be heading in our direction.
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| The Earth's magnetosphere buffers the effects of the solar flare. Click image to enlarge. |
This solar flare was far from a one off. Coronal Mass Ejections are a common occurrence on the Sun’s surface, typically releasing up to 60 yottajoules (that’s 60000000000000000000000 kilojoules) of energy - more than a thousand times our annual global energy consumption.
What causes a solar flare?
Like the Earth, the Sun has a North and South Pole with magnetic field lines running through it. Unlike the Earth, however, the Sun also has powerful convective currents caused by rising superheated matter being replaced by comparatively cooler matter. When these currents run opposite to the Sun’s magnetic field lines, they are pushed back down below the surface, leaving comparatively chillier matter - a mere 3,500oC compared to a balmier 5,500oC in surrounding areas - on top.
The cool patches appear as dark splodges – sunspots – which, typically, are the size of the Earth. In these areas the Sun’s magnetic fields are particularly gnarled and twisted; like taught elastic bands, the magnetic fields can snap back and reverse, resulting in the release of vast quantities of energy and expulsion of plasma heated to 10 million degrees. Ionised particles shoot out like bolts of electricity travelling at nearly the speed of light for vast distances.
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| The plasma expelled in a flare is heated to 10 million degrees Celsius. Click to go to the solar flare gallery. |
The Sun is believed to have a 22 year cycle of activity, with eleven year peaks lasting for one to two years. During peak periods, sunspots and associated planet-sized coronal mass ejections occur with their greatest frequency; new ones appearing daily on the Sun’s surface.
From ejection, the flares take six to nine hours to reach us on Earth. Power providers, satellite system operators and military radar detectors need to be prepared for disruption and aeroplanes may need to alter their flight paths to avoid increased doses of ionising radiation that are given off by the charged particles of the solar winds.
Migratory animals with inbuilt compasses, like pigeons, dolphins and whales, also suffer during the electrical storms on Earth. They can get hopelessly disorientated and end up miles from their intended destination. Imagine you’re trying to follow a map; it’s as though when you look up from the page, all the roads have been twisted up and nothing matches the image on the paper.
Keeping an eye on the Sun
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| What is an astronomical unit. Click to enlarge. |
Ulysses first flew over the Sun's poles in 1994 and 1996, during a period of low solar activity. In March 2000, Ulysses detected the Sun’s south magnetic pole gradually fading over a month long period until, in 2001, the poles flipped direction, coinciding with a return to large amounts of activity on the Sun’s surface.
For now things are quiet, but we are probably approaching a second peak. In 2006 NASA researchers announced that the next cycle would be the strongest since 1958, when the northern lights (normally only seen at the North Pole) could be seen as far south as Mexico. But as the activity of the Sun keeps changing, the predictions keep altering.
Last year Japan launched a Sun microscope ‘Solar B’, and months later NASA launched its Stereo mission - twin spacecraft that will make 3D observations of the Sun.
At last we are gaining a better understanding of what’s going on in the Sun. We have the means to keep our technology safe from solar storms, by predicting and making changes. Even though sometimes that just involves sitting out the storm.
The world's space agencies have been taking some amazing images and video of solar flares in recent years. Go to our solar flare gallery to see some of the best.
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Title Image: NASA
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