SPACE – Earth, a rocky, watery oasis in the universe, is an ideal place for life to thrive for a variety of reasons. We are at the right distance from our star for liquid water to exist on the planet’s surface. The gravitational pull of other large planets also protects us from apocalyptic collisions with millions of stray meteorites.
Then there is a magnetic field that surrounds the Earth with a layer that protects us from charged particles that slide freely through space. So, we will discuss this magnetic field next.
Earth’s magnetic field is generated by a complex flow of liquid metallic material in the planet’s outer core. The flow of material, influenced by the Earth’s rotation and the presence of a solid iron core, produces a dipolar magnetic field. Its axis is approximately parallel to the planet’s rotation axis.
Hidden in the chemical composition of ancient rocks are clues that demonstrate that the Earth’s magnetic field is a dynamic and changing phenomenon. The cooling magma, rich in iron minerals, is pulled parallel to the Earth’s magnetic field, similar to how a compass needle is pulled north. Research on ancient geomagnetic fields recorded in rocks is the subject of the scientific discipline of paleomagnetism.
Read also: Why does the Earth have magnetic poles?
Paleomagnetic research shows that the Earth’s magnetic field has changed and even reversed its polarity many times in the geological past. So, what causes the magnetic poles to flip?
Earth’s magnetic field varies on very short and long time scales, from milliseconds to millions of years. The interaction of magnetic fields with charged particles in space can change them in short periods of time. Meanwhile, disturbances in the magnetic field over longer periods are usually caused by internal processes in the Earth’s liquid outer core.
“Secular variations in the geomagnetic field result from the advection effect of the magnetic field by flows in the outer core of the fluid and the diffusion effect of the magnetic field in the Earth’s core and mantle,” the geophysicist Leonardo Sagnotti.
Several times in the past, magnetic field fluctuations due to the movement of metallic material in the outer core have caused a complete reversal of the polarity of Earth’s magnetic field. Previous research on the state of the magnetic field stated that there are two possible states of polarity. First, the current situation, where magnetic field lines enter the center of the Earth in the Northern Hemisphere and exit outward from the Earth in the Southern Hemisphere. The second polarity is the opposite one, which can also be as stable as the current state.
Read also: Strange radio signals from Earth-like planets, alleged magnetic fields, requirements for life
Paleomagnetic studies show that polarity reversals in the Earth’s magnetic field are not periodic and cannot be predicted. “The flow of liquid metal (mainly liquid iron) in the Earth’s outer core is chaotic and turbulent. The polarity reversal occurs during periods of low geomagnetic field intensity, where the intensity of the dipolar component decreases dramatically and the spatial structure is unstable,” Sagnotti said. Geologically, periods of polarity reversal occur in an instant, with periods up to several thousand years.
The effect of magnetic pole reversals on life on Earth
When the magnetic field tends to reverse, its intensity decreases, leaving the Earth’s atmosphere more exposed to solar wind and cosmic rays in the form of charged particles. Recently, a study showed that during the Laschamps trip, i.e. a period of low magnetic field intensity 41,000 years ago, the flux (flux) of cosmic rays entering the Earth’s atmosphere was three times higher than today.
To date, there is no significant evidence of a correlation between the mass extinction of life on Earth and the reversal of geomagnetic polarity. However, linking species extinction and speciation rates to periods of low magnetic field intensity is hampered by uncertainties in the time scale of magnetic rotation.
2024-01-23 21:34:00
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