Australian geophysicists have discovered an unusual structure deep within the Earth’s liquid core. It runs parallel to the equator and is only visible at low latitudes. The discovery will lead to a better understanding of the dynamics of the planet’s magnetic field.

The Earth’s core is divided into a solid inner part and a liquid outer part. On top is the mantle, covered with the crust. Scientists from the Australian National University have found a previously unknown structure in the outer core, closer to the mantle boundary. Information about it is published at: Science DevelopmentsAccording to co-author of the study, Professor Hrvoje Tkalčich, the new structure emerged as a result of the slowing down of seismic waves.

“It is located parallel to the equatorial plane, is confined to lower latitudes and has a ring shape. We do not know its exact thickness, but we assume that the ‘doughnut’ extends for the first hundreds of kilometers below the boundary between the mantle and the core,” Tkalchich explained.

To study the internal structure of the Earth, seismic tomography helps measure the speed of seismic waves after shock events, most often earthquakes, whose centers can reach depths of 700 kilometers.

Earthquakes produce deformation waves that spread throughout the planet. These are recorded by seismographs placed on Earth. Changes in seismic wave speeds indicate heterogeneity in the layer. Geophysicists usually record the speed of seismic waves in the first hours after an earthquake. This time the signals are recorded for much longer.

“By studying the geometry of the seismic waves, their trajectory in the outer core, we reconstructed their speed and saw the area where they slowed down. In the studies conducted, it was not found yet because the data collected did not cover a sufficient volume of the outer core, since the recordings were made within an hour after the earthquake. Since we studied the reflected waves hours after the big earthquake, we covered a larger area,” Tkalchicha explained.

The discovery by Australian geophysicists provides new insights into the dynamics of the Earth’s magnetic field, according to co-author Xiaolong Ma.

“For scientists, the outer core is still mysterious, there is much to discover. This requires combining the efforts of seismology, mineral physics, geomagnetism and geodynamics,” Ma emphasized.

The outer core is composed primarily of molten iron and nickel. The energetic movements of the electrically conductive mass create a magnetic field that protects the planet from the effects of cosmic radiation and helps support life.

Knowledge of the composition of the outer core will help understand the behavior of the magnetic field, which scientists assume may disappear or weaken.

“Based on the fact that the speed of seismic waves slows down in an open structure, it can be assumed that it is enriched with light chemical elements. The difference in composition and temperatures increases the mixing in the outer core,” added Professor Tkalchich.

According to the geophysicist, the new study will also be useful in relation to the magnetic fields of other planets.