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30/07/2014

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Zombie satellites and power failures: the impact of space weather

By Helen Bridle

Due to our reliance on technology, the hazards to society from extreme space weather are higher than at any point in human history, the British Science Festival heard yesterday.
 
The sun periodically ejects twisted bits of magnetic field known as coronal mass ejections. If these reach Earth, colliding with our planet’s surrounding geomagnetic field, the result is geomagnetic storms which could disrupt electricity transmission, communications and satellites.
 
Dr Lucie Green from the Mullard Space Science Laboratory said: “Our sun is not the placid yellow disc we see from Earth but a variable and dynamic star. It is reaching its 11-year height of activity in the next couple of years and we need to focus on what this might mean for us and the technology we rely on.”
 
Satellites orbit the Earth at a particular distance, just inside a radiation belt. Extreme space weather can increase the number of killer electrons in the radiation belt and swell the belt such that it overlaps the satellite orbit.
 
The high-speed killer electrons pass through satellites, potentially disturbing their function, sometimes leading to “zombie” satellites. The zombies cease to function, disrupting phone calls and TV signals, and merely clutter up the orbit causing problems for other satellites.
 
Solar ejections reaching Earth can also damage high voltage power grids, like the 1989 Hydro-Quebec shutdown of the entire grid or the 2003 Halloween Storm which caused two UK transformers to fail.
 
The sun is monitored every 10 seconds so scientists know what is coming, giving us some warning. Slow eruptions take three days to reach the Earth, whereas fast ones can be here in less than 24 hours.
 
The problem is to predict the extent of the effect, which depends upon the relative orientations of magnetic fields of the coronal mass ejection (CME) and the Earth when they collide. The CME changes orientation as it travels through space and imaging only shows a ball of hot gas heading towards us.
 
The information about magnetic fields is obtained from satellites about 100 million miles from Earth giving only 30 mins to one hour of warning.
 
Dr Alan Thompson, Head of Geomagnetism at the British Geological Survey, recommended engineers build in resilience to space weather in our power and communications infrastructure in the same way that we would design our built environment to cope with other natural phenomena, like hurricanes.


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