Earth, our rocky, watery oasis in the universe, is an ideal place for life to develop for several reasons.
We sit at just the right distance from our parent star for liquid water to exist on the planet’s surface. The gravitational pull of other large planets helps protect us from apocalyptic collisions with stray asteroids. And the planet’s magnetic field surrounds Earth with a protective barrier that protects us from charged particles hurtling through space.
Earth’s magnetic field is produced by the complex flow of molten metallic material in the planet’s outer core. The flow of this material is affected by both the Earth’s rotation and the presence of a solid iron core; This results in a bipolar magnetic field in which the axis is roughly aligned with the planet’s rotation axis.
Hidden in the chemical composition of ancient rocks are clues that the Earth’s magnetic field is a dynamic, changing phenomenon. Cooling magma, rich in iron minerals, is pulled into line with the Earth’s magnetic field, similar to the needle on a compass being pulled to point north. The study of ancient geomagnetic fields recorded in rocks is the subject of a discipline known as “paleomagnetism”.
Paleomagnetic studies have provided scientists with the knowledge that the Earth’s magnetic field has changed polarity and even reversed many times in the geological past. But why?
Relating to: Earth’s magnetic field: Explained
What causes magnetic poles to rotate?
The Earth’s magnetic field varies over very short and extremely long time scales, from milliseconds to millions of years. The interaction of the magnetic field with charged particles in space can change it on short time scales, while on longer time scales perturbations in the magnetic field are caused by internal processes occurring in the Earth’s outer liquid core.
“The secular variation of the geomagnetic field results from the steering effect of the magnetic field by the flow in the liquid outer core and the effects of magnetic field diffusion in the core and mantle,” geophysicist Leonardo Sagnotti told Space.com.
Fluctuations in the magnetic field due to the movement of metallic material in the outer core have caused a complete reversal of the polarity of the magnetic field in the Earth’s past. Paleomagnetic studies examining the previous states of the magnetic field have shown that there are two possible states of polarity; the current ‘normal’ situation in which the field’s lines of force move in and out of the Earth’s center in the northern hemisphere. extraterrestrial in the southern hemisphere. Reverse or ‘reverse’ polarity is equally possible and stable.
Paleomagnetic studies have shown that pole shifts in the Earth’s magnetic field are not periodic and cannot be predicted. This is largely due to the behavior of the mechanisms responsible for this.
“The flow of metallic fluid (mostly molten iron) in the Earth’s outer core is chaotic and turbulent. Polarity shifts occur during periods of low geomagnetic field intensity, when the intensity of the dipolar component is greatly reduced, and the field is unstable,” says Sagnotti.
The transient period of polar reversal occurs geologically instantaneous (i.e., below geological resolution) and spanning up to several thousand years.
How does shifting magnetic poles affect life on Earth?
When the magnetic field tends to flip, it is in a reduced density, causing the Earth’s atmosphere to be more exposed to the solar wind and cosmic rays in the form of charged particles. A recent study showed that: trip to LaschampsDuring a period of low magnetic field strength that occurred only 41,000 years ago, the global cosmic ray flux reaching the Earth’s atmosphere increased to three times its current value.
Currently, there is no significant evidence of a correlation between the mass extinction of life on Earth and the reversal of geomagnetic poles. However, relating species extinction and speciation rates to periods of low magnetic field intensity is hampered by uncertainties in the known timeline of these magnetic ‘reversals’.
In addition, magnetic reversals occur frequently on geological time scales (several hundred times in the last 160 million years), while recorded mass extinction events occur approximately every hundred million years (much less frequently).
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From the perspective of human civilization, it is not the change of magnetic poles that is directly relevant, but the resulting decrease in the geomagnetic field intensity. Society is becoming increasingly dependent on technology, and the effects of decreasing magnetic field intensity should be seriously considered by governments and international organizations.
“In this configuration, there will be a significant increase in the penetration of charged particles into the magnetosphere at altitudes closer to the Earth’s surface, which will have significant repercussions on our technological world,” adds Sagnotti.
The risks to our planet and civilization can have significant impacts on civil society, trade, security, communications, energy infrastructure, satellites, and the lives of people in low Earth orbit. Unfortunately, the erratic nature of magnetic shifts and reversals means we cannot predict exactly when this will happen; All we know is that it will happen.