Nasa has warned that a peak in the sun's magnetic energy cycle and the number of sun spots or flares around 2013 could generate huge radiation levels.

The resulting solar storm could cause a geomagnetic storm on Earth, knocking out electricity grids around the world for hours, days, or even months, bringing much of normal life grinding to a halt.

Defence Secretary Liam Fox, who delivered the keynote address at an international conference on the vulnerability of electricity grids around the world, warned that modern societies' dependence on technology leaves them vulnerable to such events.

 Massive Solar flare 2012 / 2013 predictions?

The Sun follows an 11-year cycle of high and low periods of solar activity. It is now leaving a notably quiet phase and scientists expect to see a sharp increase in the number of solar flares as well as unprecedented levels of magnetic energy.

The rings of fire, which have the power of 100 hydrogen bombs, could cause twenty times more economic damage than Hurricane Katrina.

Experts met in Washington DC in June to discuss how to protect Earth from the ferocious flares, which are expected sometime around 2013.

Nasa is using dozens of satellites – including the Solar Dynamics Observatory – to study the threat.

The problem was investigated in depth two years ago by the National Academy of Sciences, in a report which outlined the social and economic impacts of severe space weather events.

It noted how people of the 21st-century rely on high-tech systems for the basics of daily life.

Smart power grids, GPS navigation, air travel, financial services and emergency radio communications can all be knocked out by intense solar activity.

But much of the damage could  be minimised if it was known in advance that the storm was approaching.

Putting satellites in 'safe mode' and disconnecting transformers could  protect them from damaging electrical surges.

 

This graphic shows how the sun's solar flares could endanger human life by interfering with high-tech systems such as satellites and power grids

Scientists are said to fear that a similar effect could be achieved by a hostile power exploding a nuclear weapon in space, producing a massive burst of electromagnetic energy known as a high altitude electromagnetic pulse.

Mr Fox also  warned that countries seeking nuclear capabilities could use them in a different way to the traditional 'nuclear strike" method used on Hiroshima and Nagasaki during the Second World War.

Citing North Korea and Iran, Dr Fox said countries seeking nuclear capabilities could use them in a different way to the traditional 'nuclear strike' method used on Hiroshima and Nagasaki during the Second World War.

This could involve a nuclear detonation in the upper atmosphere that would knock out vital electronic systems by producing an electro-magnetic pulse, he said.

He warned that terrorists might also seek to employ similar methods as he urged the public to take greater heed of the threat.

'I think it's a subject that we need to give a good deal more attention to, not least because we are in an era where there are those who seem to believe that we can choose to enter or not enter certain conflicts, and also because we live in a war where proliferation is becoming more not less the case,' the Defence Secretary said.

'And when we are discussing North Korea or Iran, for example, people need to understand there are other risks than just what we would consider the sort of nuclear strike we saw in Nagasaki or Hiroshima.

'The range of risks out there are many-fold and I think we need to make that extremely apparent to the public.'

Dr Fox insisted that the threat of such an attack was 'low', but that the Government was working internationally with telecoms, energy and transport companies to increase resilience.

'With reliance, for instance on technology, comes vulnerability, and vulnerability can invite attack,' he went on.

'Our wider reliance on digital technologies will not have gone unnoticed among those who would mean us harm.

'We will need to ensure that those same technological innovations that provide advantage do not become our Achilles heel.'