The Earth is unique in the world solar system for several reasons: it is the only planet with a breathable oxygen atmosphere, it is covered in liquid water and it is the only celestial body (to our knowledge) to support life. However, an often overlooked feature that makes our planet special is that it is the only rocky body in the inner solar system with strong magnetic poles – your compass would be useless on Mars.
But where do these poles come from and what are they for? To answer these questions, let’s start with a trip to the center of our planet.
The Earth’s core is separated into two layers: the solid inner core and the molten metal outer core. The two layers are made of a cocktail of magnetic iron and nickel, with a few touches of lighter elements, like oxygen, silicon and sulfur.
The inner core is extremely dense and hot, like a giant glowing marble. But the outer core is fluid and swirls around this solid mass with its own convective current. It is this constant convection which generates the earth’s magnetic field, Jean Tardunogeophysicist at the University of Rochester in New York, told Live Science.
Related: What if the Earth’s magnetic field disappeared?
As heat from the inner core continually radiates to the outer core, it encounters material cooled by plate tectonic activity. This cycle causes convection, giving rise to what is called the geodynamo which produces the magnetic field.
Other planets, such as Mars and Venus, do not have magnetic fields, in part because they lack magnetic fields. tectonic plates. Evidence suggests that these planets may once have had autonomous geodynamos but that they died out for unknown reasons. Mercury has a weak magnetic field, but it is only 1.1% as strong as Earth’s and does little to protect the planet from solar radiation.
As the liquid metal circulates in Earth’s outer core, its movement and high iron content cause the planet to behave like a huge dipole magnet, with one negatively charged pole and one positively charged pole. About 80% of the Earth’s magnetic field is organized this way, but the remaining 20% is non-dipolar; Rather than forming parallel bands of magnetic force, there are certain regions where the field swirls and behaves “like weather patterns that float,” Tarduno said.
These irregular patterns produce strange spots in the magnetic field – places like the South Atlantic anomaly, a vast swath of the Atlantic Ocean where the intensity of Earth’s magnetosphere drops dramatically. Researchers think this “bump” in the magnetic field results from unusual tectonic activity under Africa. Areas like the South Atlantic Anomaly are fascinating, but they are also concerning, for several reasons.
“The magnetosphere is like a protective envelope” Joshua Feinberg, a geologist specializing in paleomagnetism at the University of Minnesota, told Live Science. It helps deflect huge amounts of dangerous solar radiation Earth, acting like a layer of sunscreen on a planetary scale. In areas where the magnetosphere is weak, additional doses of radiation escape, potentially contributing to higher rates of skin cancer.
“Another concern is the effect on satellites,” Tarduno said. Bursts of solar radiation called coronal mass ejections can knock out satellites and other spacecraft if they are not protected by the Earth’s magnetic field. This can have catastrophic effects on telecommunications, internet access and GPS services in areas affected by anomalies.
The South Atlantic anomaly could be 11 million years old, according to an article published in 2020 in the journal PNASand this could be linked to another planetary magnetic field phenomenon: pole reversal.
The history of the Earth’s magnetic field is written in ancient lava flows and deep-sea sediments. These types of rock materials are rich in magnetic metal fragments, such as tiny shards of iron, that orient themselves along magnetic field lines. “Eventually, this original alignment is locked into the sediments, and we get these deep-time records of how the Earth’s magnetic field was oriented,” Feinberg said.
Thanks to these recordings, scientists know that our planet’s magnetic poles are drifting over time. Currently, the geographic North Pole is approximately 310 miles (500 kilometers) away far from its corresponding magnetic pole (which is technically magnetic south, for now). And about every 300,000 years, the poles suddenly flip, reversing magnetic north and south, according to NASA.
However, paleogeomagnetic records show that a complete pole reversal this hasn’t happened in about 780,000 years. Some researchers think this means that we have to do a flip – and that the strength of the South Atlantic anomaly could indicate that we are close.
If the poles were to reverse, Earth’s magnetic field would drop to 20%, perhaps for centuries. Such an event would throw our current global communications system into disarray. However, other studies suggest that a reversal is not imminent.
Either way, Feinberg said, studying our planet’s interior and paleogeomagnetic records will help us understand the complex interaction between the magnetosphere and life on Earth — and perhaps help us understand prepare for future changes.
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