Solar bursts threaten to knock out power grids
31 March 2001
Satellite and radio signals, and electricity power grids, could be disrupted
by a huge outpouring of energy from the Sun this week.
Two "coronal mass ejections", containing as much energy as thousands of
atomic bombs, exploded from the surface of the Sun earlier this week, after
building up near the biggest sunspot seen on the star for the past decade.
Now scientists believe there is a significant chance that on arriving due
last night or today they could knock out sensitive electromagnetic systems
orbiting the Earth, disrupt the ionosphere, which bounces radio waves around
the globe, and even affect power lines at ground level.
Dr Steve Fossey, of the Mill Hill Observatory at University College London,
said: "Satellites are at risk because these ejections contain highly charged
electromagnetic particles, which can knock out the components inside them. It
can also affect the ionosphere, which could cause the aurorae, or northern
lights."
Sunspots appear and disappear on the Sun in an 11-year cycle that is now at
its climax marked by the magnetic poles of the star flipping over, so that
its magnetic "north" becomes south and vice-versa. Dr Fossey said: "The
flipping happened in February, which marks the solar maximum."
The associated coronal mass ejections are billion-ton clouds of electrified,
magnetic gas that solar eruptions hurl into space at speeds ranging from a
few hundred to 2,000 kilometres per second (4.5 million mph). The latest have
been thrown out from the surface near Noaa 9393, a sunspot that first
appeared a month ago on the Sun's surface and that is so large that it is
visible with the naked eye though nobody should look directly at the Sun,
because that would cause immediate and permanent damage to the eye.
Sunspots appear black against the Sun's surface; they are actually cooler
than their surroundings about 3,000C rather than 5,500C. Scientists reckon
they are caused when magnetic fields below the star's surface reach the
exterior, where the motion creates a huge store of magnetic energy that is
eventually released in an explosive coronal mass ejection.
Some astronomers think that the two ejections from earlier this week will be
followed by more intense ones from Noaa 9393. Joe Elrod, of the US National
Solar Observatory at Sacramento, New Mexico, said: "The two small flares may
be the precursors to the big one."
