Earth’s magnetic field is one of the fundamental forces that enable the existence life on the planet. The generation of the magnetic field has been attributed to geodynamo, the movement of the liquid iron in the outer core of the Earth. However, the origin of the magnetic force and its history has remained a mystery for the researchers. A research team from the Carnegie, headed by Alexander Goncharov, has attempted to explain this geological phenomenon from a historical perspective.
Rocky materials around the sun coalesced to form the Earth. With the passage of time, the denser materials, including iron, sank downwards and created the layered structure of the Earth i.e. the core, mantle and the crust. While the innermost core of the Earth eventually turned solid, the outer core is still liquid iron alloy. It is the motion of this liquid iron alloy that generates the magnetic field.
To understand the evolution of the magnetic field and the source of energy required to sustain it, it is necessary to explain the process of heat conduction from the solid inner core, to the molten outer core. The problem is compounded by the fact that the extreme pressure and temperature inside the Earth’s core imply a different behavior as compared to the surface behavior of these materials. Commenting on the driving force behind this project, Goncharov said:
“We sensed a pressing need for direct thermal conductivity measurements of core materials under conditions relevant to the core. Because, of course, it is impossible for us to reach anywhere close to Earth’s core and take samples for ourselves.”
The researchers employed the laser-heated diamond anvil cell to emulate the conditions of the inner core of the Earth. The study focused on the heat conduction properties and mechanism of iron in these conditions. The equipment is a cutting edge tool which squeezes a small amount of material between the two diamonds thus, creating the same pressure as that experienced in the core. The material is heated by a laser to the specified temperatures.
The investigating team studied the samples of iron across a range of varying temperatures and pressure according to the size of various planets in the solar system, from Mercury to the Earth. The vast range of temperature and pressure varied across 345,000 to 1.3 million times normal atmospheric pressure and 2,400 to 4,900 degrees Fahrenheit respectively.
The results of the study helped the scientists to hypothesize that the energy required to sustain the geodynamo had been present in the Earth’s geographical structure soon after its birth. The iron samples were able to transmit energy between 18 to 44 watts per meter.
Goncharov is now planning to study the behavior of the materials other than iron in the core. The objective is to understand the thermal processes occurring inside the core of the Earth.