Radio Silence
Published: 14 August 2006 03:00 PM
Industry Channel: Communications
Source: The Engineer Online
http://www.e4engineering.com/Articles/295732/Radio%20silence.htm-----------------------------------------
A proposed US system to protect satellites from solar storms or high-altitude nuclear detonations would cause worldwide radio communications blackouts, according to new research by a group of scientists from New Zealand, Finland and the UK.
If activated, the envisaged "radiation belt remediation" system would significantly alter the upper atmosphere in the short term, seriously disrupting high frequency (HF) radio wave transmissions and GPS navigation around the globe, said the group's lead researcher, Dr Craig Rodger of the University of Otago Physics Department.
The remediation system aims to protect hundreds of low earth-orbiting satellites from having their onboard electronics ruined by charged particles in unusually intense radiation belts "pumped up" by high-altitude nuclear explosions or powerful solar storms, said Dr Rodger.
The approach, which is being considered by the US Air Force and the US Defense Advanced Research Projects Agency, involves using very low frequency radio waves to flush particles from belts and dump them into the upper atmosphere over either one or several days.
‘We've calculated that Earth's upper atmosphere would be dramatically affected by such a system, causing unusually intense HF blackouts around most of the world,’ he said.
‘Airplane pilots and ships would lose radio contact and some Pacific Island nations could be isolated for as long as six to seven days, depending on the system's design and how it was operated,’ he said.
GPS would likely also suffer large-scale disruptions, as signals between ground users and satellites were scrambled by the ionosphere, he added.
The disruptions result from a deluge of dumped charged particles temporarily changing the ionosphere from a "mirror" that bounces high frequency radio waves around the planet to a "sponge" that soaks them up, he said.
In their paper, just published in the August edition of the international journal Annales Geophysicae, the Otago researchers and UK and Finnish colleagues suggest that policymakers need to carefully consider the implications of remediation.
‘If the intense radiation belts resulted from a rogue state detonating a nuclear-tipped missile in the upper atmosphere, using such remediation technology would probably be acceptable to the international community, regardless of the side effects we foresee.
‘However, the case for using the system to mitigate the lesser risk to satellites from charged particles injected by naturally-occurring solar storms needs to be considered more closely. Here, the impact of the disruption to global communications should be weighed carefully against the potential gains,’ said Dr Rodger.
The researchers also calculated the likely effect of remediation on the ozone layer, but found that ozone depletion would be short-lived and similar to that resulting from natural processes such as large solar storms and volcanic eruptions.
The paper, titled: ‘The atmospheric implications of radiation belt remediation’ was co-authored with Otago colleague Associate Professor Neil Thomson and researchers from the British Antarctic Survey, and the Sodankylä Geophysical Observatory in Finland and the Finnish Meteorological Institute.
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