From: Andy Soos, ENN
Published February 25, 2011 11:43 AM

The Gerat Northern Lights

An aurora is a natural light display in the sky, particularly in the polar regions, caused by the collision of charged particles directed by the Earth's magnetic field. An aurora is usually observed at night and typically occurs in the ionosphere. It is also referred to as a polar aurora or, collectively, as polar lights. These phenomena are commonly visible between 60 and 72 degrees north and south latitudes, which place them in a ring just within the Arctic and Antarctic polar circles. Recent increases in solar activity, including the largest solar flare in four years, may lead to hopes of seeing the aurora borealis, also known as the northern lights, in the United Kingdom and other relatively more southern locales. In the United Kingdom, for example, the chances of seeing the aurora increase the further north you go — ranging from one or two displays every 10 years in the south of England to one or two displays a week in the far northern Shetland Islands. Solar variation is the change in the amount of radiation emitted by the Sun and in its spectral distribution over years to millennia. These variations have periodic components, the main one being the approximately 11-year solar cycle (or sunspot cycle). This variation causes the northern lights to vary in location and magnitude.

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Solar activity, which varies over an 11-year cycle, has been very low over the last few years. The events of recent days show that solar activity is just starting to pick up and is expected to reach the next maximum in 2013. Large solar storms are most common around the maximum in the solar cycle so the chances of seeing the aurora in more southern latitudes will increase over the next few years.

The solar cycle was discovered in 1843 by Samuel Heinrich Schwabe, who after 17 years of observations noticed a periodic variation in the average number of sunspots seen from year to year on the solar disk.

Cycles as short as 9 years and as long as 14 years have been observed. Significant variations in amplitude also occur. Solar maximum and solar minimum refer respectively to epochs of maximum and minimum sunspot counts. Individual sunspot cycles are partitioned from one minimum to the next.

Enhanced solar activity is also associated with more hostile conditions in the near-Earth space environment. Such dangerous space weather conditions have the potential to damage satellites, disrupt electrical power networks on the ground, communications with aircraft on polar routes, and GPS navigation signals. These systems will all be at greater risk over the next few years as the Sun approaches its next maximum in the solar cycle.

So as the lights brighten, signals such as cell phones may get lost in the static.

Scientists at British Antarctic Survey (BAS) operate a range of instruments that contribute to a world-wide space weather observation network. For example, on this occasion, the arrival of the coronal mass ejection associated with the recent solar flare was detected by the sudden increase in the Earth’s magnetic field at Rothera, Antarctica, on 18th February 2011.

For further information:  http://www.antarctica.ac.uk/about_bas/news/news_story.php?id=1408

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