View of the solar eruption from the SOHO satellite on August 16.
Credit: NASA/ESA
SYDNEY, 24 August 2006: An increase in sunspot activity in early August and a large solar flare on August 17 are evidence the Sun is on the verge of entering a new cycle of high activity, according to NASA scientists.
The Sun follows a regular 11 year cycle of activity, with increased frequency of sunspots, solar flares and coronal mass ejections (CME) around the time of 'solar maximum', the last of which occurred in 2001.
The Sun is currently in a time of minimum activity, although the appearance of sunspots, including a rare magnetically-reversed sunspot on July 31, indicate that the cycle of activity is due to begin to ramp up again towards the next peak, which is expected to occur in 2012.
NASA scientists observed the most recent sunspot, called Active Region 904, with intense interest using the Solar and Heliospheric Observatory (SOHO) satellite, which lingers in the gravity-netural L1 Lagrange point between the Earth and the Sun.
After watching the sunspot rotate into view on August 9, it finally popped off a modest (C-class) flare and associated coronal mass ejection (CME) on August 17 when it had rotated into a location where it practically faced Earth.
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Image: Markku Hirvenoja
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Solar flares and CMEs - their accompanying giant clouds of plasma in space - are the largest explosions in the Solar System and can pack the force of a billion megatonne nuclear bombs. They are caused by the buildup and sudden release of magnetic stress in the solar atmosphere above the giant magnetic poles we see as sunspots.
CMEs can cause problems here on Earth. The increase in cosmic radiation can interfere with satellite communications as well as disrupt powerlines here on the surface. CMEs are also a serious health threat to astronauts in orbit.
The increase in sunspots and associated cosmic radiation triggered a stunning series of auroras two and three days later. Auroras are caused when solar particles and magnetic fields pump energy into the Earth's own magnetic field, accelerating electrically charged particles trapped within.
The high-speed particles are channelled by the Earth's magnetic field towards the northern and southern poles and collide with the Earth's upper atmosphere, the ionosphere. This causes the colourful and eerie glow in the skies.
