UPDATE: From Greg Laden's blog: The story was misreported.
Is the Earth's magnetic field caused affected by ocean currents, and not its massive molten core, as is generally thought? Gregory Ryskin, associate professor of chemical and biological engineering at Northwestern University in Illinois, thinks that the motion of salty seawater generates electromagnetic waves. His paper will be published by Britain's Institute of Physics's New Journal of Physics.
Earth's magnetic field is vital for life, extending tens of thousands of miles into space and protecting the planet against radiation that would otherwise burn away the atmosphere and oceans.
Existing theories explain Earth's magnetism by suggesting that the centre of the planet comprises a white-hot solid iron ball about 1,500 miles in diameter, surrounded by an outer shell of liquid metal a further 1,400 miles thick.