Forecasters keep eye on looming 'Solar Max'
The coming year will be an important one for space weather as the Sun pulls out of a trough of low activity and heads into a long-awaited and possibly destructive period of turbulence. Many people may be surprised to learn that the Sun, rather than burn with faultless consistency, goes through moments of calm and tempest.
But two centuries of observing sunspots -- dark, relatively cool marks on the solar face linked to mighty magnetic forces -- have revealed that our star follows a roughly 11-year cycle of behaviour.
The latest cycle began in 1996 and for reasons which are unclear has taken longer than expected to end.
Now, though, there are more and more signs that the Sun is shaking off its torpor and building towards "Solar Max," or the cycle's climax, say experts.
"The latest prediction looks at around midway 2013 as being the maximum phase of the solar cycle," said Joe Kunches of NASA's Space Weather Prediction Center.
But there is a prolonged period of high activity, "more like a season, lasting about two and a half years," either side of the peak, he cautioned.
At its angriest, the Sun can vomit forth tides of electromagnetic radiation and charged matter known as coronal mass ejections, or CMEs.
This shock wave may take several days to reach Earth. When it arrives, it compresses the planet's protective magnetic field, releasing energy visible in high latitudes as shimmering auroras -- the famous Northern Lights and Southern Lights.
But CMEs are not just pretty events.
They can unleash static discharges and geomagnetic storms that can disrupt or even knock out the electronics on which our urbanised, Internet-obsessed, data-saturated society depends.
Less feared, but also a problem, are solar flares, or eruptions of super-charged protons that can reach Earth in just minutes.
In the front line are telecommunications satellites in geostationary orbit, at an altitude of 36,000 kilometres (22,500 miles) and Global Positioning System (GPS) satellites, on which modern airliners and ships depend for navigation, which orbit at 20,000 kms (12,000 miles). . Click Here for more info.
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