Earth's Magnetism and the Geodynamo Paradox
Earth’s magnetic field is one of the reasons our planet is inhabitable. Without the protection of magnetism, Earth would face the dangers of space like cosmic radiation, which would be catastrophic for life on the surface. While we understand the basic process powering the magnetic field, the origins and evolution of our magnetic bubble are a little unclear. So, what processes sustain the magnetic field and how did it evolve?
The Geodynamo Effect
At Earth’s core, there is a solid inner layer consisting of iron where the estimated temperature is 9,800 degrees Fahrenheit. The heat from the inner core is transferred through conduction to the outer core, which consists of liquid iron alloy. The geodynamo is powered in part by the convection or transfer of heat in the outer core and in part by the rotation of the planet. This phenomenon called the geodynamo effect generates Earth’s magnetic field.
The Geodynamo Paradox
The paradox of the geodynamo is that according to theoretical analyses, the thermal conductivity of iron at the core is 150 watts per meter per kelvin. However, this high amount of conductivity is impossible because it leaves little energy left to power convection. It also only supports the existence of the geodynamo for about 1 billions years whereas other studies show that 3.4 billion years is a more accurate estimate for its lifespan.
So, in order to determine the truth behind this paradox, scientists recreated the conditions at Earth’s core using a laser-heated diamond anvil cell. Essentially, two diamonds were used to squeeze tiny samples of iron and recreate the pressures at the core and the laser heats the sample to the proper temperature. Under these conditions, researchers were able to determine a more accurate estimate for the thermal conductivity of iron at the core. Based on their experiments, thermal conductivity is actually between 18 and 44 watts per meter per kelvin, which supports the estimated age of the dynamo effect.
Earth’s magnetism is essential to sustaining life on the planet’s surface and is one of the many reasons other planets aren’t habitable. Find out how Earth’s magnetism compares to that of other planets in our solar system!