When and where does "geomagnetic reversal" where the earth's magnetic field inverts? Investigate the mystery from traces of humanity several thousand years ago

ByNASA Goddard Space Flight Center

It is well known that the Earth is one big magnet and the geomagnetism surrounding the whole planet acts as a "barrier" that bounces off the solar wind from the sun and the cosmic rays falling from the universe. In addition, the direction of this geomagnetism is changed in long years and years, and the south pole and the north pole are opposite in the time axis of hundreds of thousands of years to millions of years "Geomagnetism reversalI know that it is happening. Research is continuing on why such facts are known, and when and where geomagnetic reversal, which is thought to occur in the future, is going to start from where.

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There are still many mysterious parts still remaining in the mechanism of the earth's magnetic field but in the latest research it is predicted that it is due to the melted iron mantle convecting inside the earth It is being viewed. Magnetism is caused by the action of the current flowing through the object, and it is becoming widely known that the entire planet is one electromagnet by the literally large current flowing on the global scale.

ByPublic Domain

And it has been clarified from years of research that this geomagnetism tends to weaken gradually. According to observational data of the geomagnetic observation satellite "SWARM" launched by the European Space Agency, it has become clear that the earth's geomagnetism is decreasing in intensity at "5% in 10 years". If the geomagnetism continues to weaken at this pace, the strength will reach zero after 2000, but this timing is also shown to be the timing of "geomagnetic reversal" timing. The most recent geomagnetic reversal that occurred on the earth is considered to be 780 thousand years ago, and it is thought that the geomagnetic reversal may occur once again from the cycle.

It turned out that the earth's magnetic field weakened faster than expected, when is the timing of geomagnetic reversal? - GIGAZINE

As well as decreasing the earth's magnetism, the poles of the geomagnetic movement are known to movePole shiftIt is a phenomenon called. This is also occurring on the present earth, and research results saying magnetic north is traveling to the east at a speed of about 64 kilometers a year is announced.

Also, the intensity of the geomagnetism is not uniform across the globe. Observations using SWARM reveal the fact that the area around the Indian Ocean, which is drawn red in the following map, has the strongest geomagnetism and the weakest area around the North American continent.

Also, in response to this geomagnetic distribution, changes are also occurring in outer space over the Earth.South Atlantic abnormal zoneThe phenomenon called, usually exists around 1000 km over the earthVan Allen beltThe altitude has declined from 300 km to 400 km in the area centered on the continental South American continent. The Van Allen Belt is a radiation zone composed of protons and electrons captured by the Earth's magnetic field, in which the radiation level is intensified. Astronauts are taking measures such as restricting extravehicular activities, as the influence of radiation appears greatly on artificial satellites and the International Space Station that fly in the vicinity and computer troubles are likely to occur.

ByPublic Domain

Current geomagnetism can be easily measured by using measuring instruments etc, but by looking at the "geomagnetic fossil (paleomagnetism)" left in the soil etc. of the past geomagnetism, what kind of state It is possible to know whether it was. This field is "Archaeomagnetism"It is an academic / technology that is also known far more than the history of human beings, which can also learn the state of the geological age.

It is possible to conduct these investigations using traces of houses made of hard pottery or clay of old age. It flows in Africa's Zimbabwe and BotswanaLimpopo RiverSurvey of the residual magnetism of ceramics found in the watershed area revealed that the geomagnetism of the area was rapidly decreasing around the year 1300 AD. This indicates that the same thing as the contemporary geomagnetic reduction occurred.

Archaeological Geomagnetism | Japan Archaeological Magnetism Database

One of the clues to predicting the timing of geomagnetic reversal is to observe the state of "core" and "mantle" existing inside the earth. The state of the core and the mantle are thought to be closely related to the state of the geomagnetism and it is thought that it is closely related to the state of the geomagnetism and it is thought that it is closely related to the state of the geomagnetism so that weather forecast is carried out by observing the state of the atmosphere and by observing the state of the interior of the earth "Geomagnetic Forecast" It is the basis of that idea to do.

However, it is impossible to closely observe the inside of the Earth on the other side of several hundred kilometers of crust. What is being used is a method of finding the internal structure of the earth by observing how the vibration generated by an earthquake or artificial explosion is transmitted "Seismic tomography"is. The interior structure of the earth has variations in density depending on places, vibration is fast in places with low density, and the speed with which vibrations are transmitted at high density will be slow. It is to know the inside of the earth using this characteristic and data such as refraction occurring at the boundary of density.

From this survey, there is abnormality in the propagation velocity of the seismic wave in the basement of a wide area mainly in Africa and the PacificLarge low-shear-velocity provinces(LLSVPs: large scale low shear rate region) existed in the region. This area is also known as "Super Plume" and is considered to be the part where the Earth's core and the lower mantle meet. When seismic waves are transmitted to this boundary layer, it is thought that wave propagation changes.

What is interesting is that the location of the LLSVPs is closer to the area where the geomagnetic decrease confirmed in the Limpopo River mentioned above. Since the structure of the Earth's interior including the mantle is considered to be greatly involved in the generation of geomagnetism, the flow of iron forming the core by the mantle changes in this area, and the occurrence of geomagnetism It is believed that it was affected and weakened.

Such changes are said to be featured especially in the Southern Hemisphere. With modern technology, it seems difficult to make "geomagnetic forecast" by observation of the mantle with high accuracy, but it is expected that the change will start to occur in the region mainly in Africa.

ByNASA Goddard Space Flight Center

in Science, Posted by darkhorse_log