Doughnut-Shaped Region in Earth's Core Advances Knowledge of Planet's Magnetic Field

Scientists from The Australian National University (ANU) have discovered a unique doughnut-shaped region located thousands of kilometers below the Earth's surface, deep within the liquid core, reports Science Daily. This finding enhances our understanding of the dynamics influencing the planet's magnetic field.

This structure is found exclusively at low latitudes and runs parallel to the equator, according to seismologists from ANU. Previously, this region had gone undetected.

Structure of Earth's Core

Earth's core consists of two layers: the solid inner core and the liquid outer core. The mantle surrounds the Earth's core. The newly identified doughnut-shaped region exists at the upper portion of the outer core, where it meets the mantle layer.

Professor Hrvoje Tkalčić, a geophysicist at ANU and co-author of the study, noted that seismic waves traverse this newly found region more slowly than elsewhere in the liquid outer core.

"The region is aligned with the equatorial plane, confined to low latitudes and takes on a doughnut shape," he explained. "The exact thickness of the doughnut remains unclear, but it extends a few hundred kilometers beneath the core-mantle boundary."

New Approach in Seismic Analysis

Interestingly, the ANU team utilized non-traditional seismic observation methods to make this discovery. Instead of focusing on seismic signals generated within an hour after earthquakes, they investigated waveforms for hours after these quakes, leading to their unique revelation.

"By understanding how the wave paths traverse through the outer core, we reconstructed travel times, illustrating that this newly discovered region has low seismic speeds," Professor Tkalčić elaborated.

Previous studies had limited volumetric coverage of the outer core; they only looked at waves recorded within an hour of large earthquakes. The ANU team’s extended analysis greatly improved this coverage.

Implications for Earth's Magnetic Field Dynamics

Dr. Xiaolong Ma, another study co-author, emphasized that this discovery sheds light on the complex dynamics of the Earth's magnetic field yet to be fully understood.

"The outer core contains unexplored mysteries, requiring coordination among fields like seismology, mineral physics, geomagnetism, and geodynamics," Dr. Ma stated.

The outer core mainly comprises liquid iron and nickel. The vigorous movements of this electrically conductive liquid are crucial for generating the Earth’s protective magnetic field. This magnetic shield is essential for life, defending against harmful solar winds and radiation.

Importance of Light Elements in Outer Core

The research suggests that understanding the outer core's composition, including the presence of lighter chemical elements, is key to comprehending the magnetic field and predicting potential changes such as weakening or cessation.

"Our findings indicate that reduced seismic velocity in the liquid core implies a high concentration of light chemical elements, which slow down seismic waves. These elements, coupled with temperature variations, contribute to movement within the outer core," Professor Tkalčić remarked.

"The magnetic field plays a critical role in sustaining life on Earth's surface."

This subject is of great interest in the scientific realm, which may lead to further research regarding Earth's magnetic field and similar phenomena on other planets.

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