Since the origin of the Earth, the magnetic field that surrounds it has never ceased to vary, while ensuring over billions of years its protective function against solar winds. These variations can go up to full inversions of the magnetic poles. This process has been repeated many times over geological time. It is, so to speak, a banal phenomenon, which occurs every 200,000 years on average, even if it is difficult to observe any regularity.
An anomaly, but no reversal in the program!
Currently, we are able to measure the intensity and orientation of the magnetic field terrestrial and to follow its evolution. However, scientists note that, for about 180 years, the intensity of the magnetic field has decreased by about 10%. A weakened magnetic field area has also begun to form in the South Atlantic off the South American coast. The presence of this anomaly raised the idea that a reverse polarity could be imminent. This could be the first inversion directly documented by mankind.
However, a new study, published in PNAS, shows that this is not the case. This type of anomaly would in fact be a recurring phenomenon over the last 9,000 years, in connection with the normal variations of the magnetic field which is generated by complex convective movements within the outer core of the Earth.
The researchers’ modeling thus led to the conclusion that the South Atlantic anomaly could probably disappear in the next 300 years, without causing a reversal of the magnetic field.
Does the South Atlantic Magnetic Anomaly herald an impending magnetic reversal?
Is a magnetic reversal of the Earth’s poles imminent? Maybe so… or maybe not. To try to find out, paleomagneticians have searched the archives of volcanic rocks of 34 past eruptions on Sainte-Hélène Island, at the heart of the South Atlantic Magnetic Anomaly.
Article of Laurent Saccopublished on August 22, 2020
The phenomenon of pole reversal fascinates, all the more so because it involves a strong temporary weakening of the intensity of the Earth’s magnetic shield. However, magnetic reversals discovered to exist more than a century ago have happened many times in the history of the Earth and there is no convincing evidence that it has, each time, profoundly modified the climate or the biosphere. Nothing really special seems to happen when the magnetic field of the Blue Planet is at its weakest, at least as long as it remains very temporary on the geological scale, which counts as a unit of time a million years. Fortunately, therefore, Mergerthe British-American sci-fi disaster film directed by Jon Amiel and released in 2003, is destined to stay on screens.
However, for some time there has been a decrease in the overall intensity of the Earth’s magnetic field and there is debate whether this is an indication of an impending magnetic reversal. If the phenomenon occurred today, it would certainly disrupt our technologically advanced civilization, based on electricity, electronics and satellites, especially in the event of a storm violent sun.
We understand quite well that the Earth’s magnetic field is the joint product of its rotation and the convection turbulent part of its core in alloy of iron and nickel which is liquid. L’VKS experience (Von Karman Sodium) even makes it possible to reproduce the self-exciting dynamo thus produced and the magnetic reversalsbut we do not yet know how to draw fine predictions on the evolution of the magnetosphere as we would for the climate and theatmospherealthough we still succeeded some prowess in this direction.
The South Atlantic Magnetic Anomaly and the Memory of the Saint Helena Volcano
For some time, some have wondered if the famous South Atlantic Magnetic Anomaly, which Futura discussed in the previous article below, was not a precursor to the reversal of the magnetic poles. Remember that this is a region of the Atlantic where there is a significant weakening of the intensity of the Earth’s magnetic field, which is normally roughly dipolar, like that of a bar magnet made of materials ferromagnetic. It is also noted that it is associated with malfunctions of nearby satellites, above this region.
In an attempt to better understand the nature and significance of this anomaly, paleomagneticians have excavated the Earth’s geomagnetic records preserved in volcanic rocks emitted on Saint Helena Island which lies in the middle of the Atlantic Anomaly. South. They have just published the results of their work in an article by the famous Proceedings of the National Academy of Sciences (PNAS).
Here is what Yael Engbers, doctoral student at the University of Liverpool and lead author of the article in PNAS : “Our study provides the first long-term analysis of the magnetic field in this region dating back millions of years. It reveals that the South Atlantic Magnetic Field Anomaly is not a singular anomaly, similar anomalies existed eight to eleven million years ago. This is the first time that the irregular behavior of the geomagnetic field in the South Atlantic region has been shown on such a long time scale. This suggests that the South Atlantic Anomaly is a recurring feature and likely not a sign of an impending reversal. Our work also reinforces previous studies that suggested a link between the South Atlantic Anomaly and anomalous seismic features in the coat lower and outer core. This brings us closer to establishing a direct link between the behavior of the geomagnetic field and the characteristics of the Earth’s interior.”.
Why does the Earth’s magnetic field weaken over the South Atlantic?
Article of Emma Hollen published on 05/26/2020
the earth’s magnetic field gradually weakens south of the Atlantic, a phenomenon that confuses more than one geophysicist. While some will argue that this is the work of the Atlanteans, the scientists are appealing to heaven.
Although invisible to our eyes, the Earth’s magnetic field plays an essential role in the preservation of life on our Blue Planet. Everything at once magnet and shield, it deflects the deadly particles of the solar winds, the last remnants of which blossom into northern Lights and austral to the poles of the planet. However, this is in the process of dwindling in a region stretching between Africa and South America, a region so well known for its magnetic anomalies that it is the subject of its own myths. In order to understand this astonishing phenomenon, scientists have turned to Swarma constellation of three minisatellites launched by ESA on 22 November 2013 to study our magnetosphere.
Cluster, a magnetic anomaly in the Atlantic
The magnetic field arises from the convection movements of the Earth’s outer core: surrounding the inner core, solidthis sphere of metal liquid, mainly composed of iron and nickel, acts like a real dynamo. The electric currents it engenders are shifting and changing. Thus, recent studies have observed the displacements of the magnetic North Pole over several tens of kilometers per year. But the South Atlantic Magnetic Anomaly (or Cluster) is somewhat different and has been questioning scientists for many decades already.
Although the overall strength of the Earth’s magnetic field has diminished over the past two centuries, the Cluster appears to be running its own course. Between 1970 and 2020, the field strength fell from 24,000 to 22,000 nanoteslas in this region, while the anomaly continues to move west at the rate of 20 kilometers every year. More recently, over the past five years, a second foyer low intensity appears to have emerged in southwest Africa, suggesting that the anomaly may be separating into two separate cells.
This visualization illustrates the evolution of the South Atlantic Magnetic Anomaly, recorded by the Swarm over the past five years. © Swarm, ESA
Pole reversal?
The existence of the Cluster calls into question the reductionist conception that one might have of the mechanics at the origin of the Earth’s magnetic field. A simple dipole model, describing an Earth acting like a magnet, not enough to explain I’emergence of these anomalies. This is why, in November 2013, ESA launched the Swarm mission, intended to explore our magnetosphere. ” We are lucky to have the Swarm satellites in orbit to study the development of the South Atlantic Anomaly, comments Jürgen Matzkafrom the German Center for Geoscience Research. The challenge now is to understand the processes causing these changes, at the heart of the Earth. »
The currently prevailing hypothesis is that of a pole reversal, an event occurring on average every 250,000 years. The last having occurred nearly 780,000 years ago, perhaps a new reversal is on the agenda. Whatever happens, the strange behaviors of the Earth’s magnetic field do not bode anything alarming for us on Earth. The only ones affected will be the satellites in low orbit, which may present some malfunctions during their passage over this mysterious area still misunderstood.
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