Scientists have known for centuries that the Earth's magnetic field is caused by electrical currents produced in the swirling mass of molten metal at the core of the planet. Understanding the process that generates and sustains these currents is a problem that has plagued physics for 400 years.
A lecturer in electrical engineering at UCD, Prof Annraoi de Paor, has found the answer. In the process, his solution can also be applied in helping explain sun spots, a celestial phenomenon also associated with magnetic fields.
The Earth's magnetic field is useful in lots of ways, says Prof de Paor. It tugs on compasses which guide ships and planes and helps to shield the Earth from harmful radiation.
Prof de Paor first came across the problem in the summer of 1998 after an exhausting day correcting undergraduate exam papers in UCD.
He stumbled across it while scanning the Internet and within a few weeks had solved an initial element of the magnetic field conundrum.
He sent the solution to the Professor of Physics at Oxford, who had posed the problem on the Web. He was astounded with the solution, Prof de Paor said. The Oxford don had never seen anything like the mathematical contortions used to solve the riddle, nor had the university's mathematics department. Prof de Paor subsequently published this solution in one of the journals of the European Geophysical Society.
He has built on his solution to define mathematically the processes that give rise to the Earth's magnetic field, and has a new research paper under peer review with an international geophysics journal. He has also given eight lectures on the topic here and in Slovakia.
As a lecturer in electronic engineering, Prof de Paor has taught students about magnetism but hadn't previously published in the field. To work out the processes occurring in the centre of the Earth, he drew on several research disciplines.
One involves control theory which examines the process of feedback in a system between a desired response and an actual response. For example, a thermostat raises the temperature when it is too cold, and reduces it when it is too hot, yet it is not necessary for the system to deliver the target temperature to enable it to work.
The unique combination of this research in control theory, as well as his work in electrical engineering and a branch of applied mathematics called Liapunov stability theory, gave Prof de Paor what he felt were the elements needed to approach this problem.
He worked on a theory proposed in 1919 by Prof Joseph Larmor, an Irishman, who held the Lucasian Chair in Mathematics at Cambridge from 1903 to 1932.
He said the Earth's magnetic field might be generated by a self-sustaining dynamic process in its core. Since then, countless physicists have tried to prove his theory. All have failed.
The Earth's core has a solid centre surrounded by molten material. This in turn is encircled by the solid mantle. Two electrical currents swirl around the core. The first is the main current, which flows perpendicular to the Earth's axis. The second originates in the core and shoots out, striking the mantle and splitting into two currents which run to the North and South Poles before returning to the centre. These electrical currents in turn produce a magnetic field.
The main difficulty involved discovering where the main current gets its energy. Prof de Paor found the second current transfers energy to the main current through a mechanism known as the Hall Effect.
This second current gets its energy from the rotation of the Earth's inner core. The magnetic field is generated by this self-sustaining dynamic process in the centre of the Earth, a process that has now been described and proven by Prof de Paor in a series of mathematical equations.