Even A Liquid Earth Core Generates A Magnetic Field

Eddie Gonzales Jr. – MessageToEagle.com – For more than 100 years, scientists puzzled over whether a stable magnetic field was already generated in Earth’s early days—when its core was still completely liquid, unlike today. Now, a team of geophysicists has shown with a simulation that this was very likely.

A (simulated) look into the Earth’s interior about a billion years ago: Intertwined magnetic field lines in the Earth’s core are connected to the Earth’s outer magnetic field. (Image: ETH Zurich / SUSTech)

Geophysicists from ETH Zurich and SUSTech, China, have demonstrated the dynamo effect of the Earth’s core in a model in which viscosity has no influence, as is physically correct for the Earth.
In the early days of the Earth, when the Earth’s core was completelywas liquid, the magnetic field was generated in a similar way to today.

This knowledge helps to better understand the history of the Earth’s magnetic field and to make more accurate predictions about its future development.
It’s a good thing Earth has a magnetic field: It protects the planet and its life from harmful cosmic radiation. Other planets in our solar system, like Mars, are constantly bombarded by charged particles that make life difficult.

Scientists explain the generation of the magnetic field using mechanisms of the dynamo theory. This theory states the following: The continuous, slow cooling of the liquid iron-nickel core maintains circular flows of liquid material in the Earth’s outer core, known as convection currents. At the same time, the Earth’s rotation deflects these currents, causing them to spiral. The convection currents generate electrical currents, which in turn generate magnetic fields and thus the bulk of the Earth’s magnetic field.

But the theory has a gap: Before the Earth’s inner core crystallized, about 1 billion years ago, the Earth’s core was completely liquid. The question is whether the magnetic field could have been generated before this time.

A team of three geophysicists from ETH Zurich and SUS Tech in China have now provided an answer in a new study in the journal Nature.

Since the Earth’s interior and the processes taking place within it cannot be observed directly, geoscientists work with computer models to study them.

The researchers have developed a model of the Earth that allows them to simulate whether a completely liquid core could also generate a stable magnetic field. Some of the simulations were run on the high-performance computer “Piz Daint” at the CSCS in Lugano.

In the simulations, the researchers demonstrate the correct physical regime in which the viscosity—the thickness—of the Earth’s core does not influence the dynamo effect. This means that the magnetic field in Earth’s early history was generated in a similar way to today.

The research team is the first to succeed in minimizing the influence of the Earth’s core viscosity to a negligible value in a model. “Until now, no one has managed to perform such calculations under these correct physical conditions,” says the study’s lead author, Yufeng Lin.

Understanding the past of the Earth’s magnetic field

“This finding helps us better understand the history of the Earth’s magnetic field and is useful in interpreting data from the geological past,” says co-author Andy Jackson, Professor of Geophysics at ETH Zurich.

The origin of life on Earth also appears in a new light: billions of years ago, it apparently benefited from the magnetic protective shield that kept out harmful radiation from space and thus made its development possible.

The researchers can also use the new findings to investigate the magnetic fields of other celestial bodies such as the sun or the planets Jupiter and Saturn.

Indispensable for modern civilizations

The Earth’s magnetic field not only protects life, but also makes satellite communications and much more in modern civilization possible. “It is therefore important to understand how the magnetic field is created, how it changes over time, and what mechanisms maintain it,” says Jackson. “If we understand how the magnetic field is generated, we can predict its future development.”

The magnetic field has changed polarity thousands of times throughout Earth’s history. In recent decades, researchers have also observed a rapid shift of the magnetic North Pole toward the geographic North Pole. Understanding how magnetism changes on Earth is essential for our civilization.

Source

Paper

Written by Eddie Gonzales  Jr. – MessageToEagle.com Staff Writer