A magnetic field surrounds the Earth and protects all living things from deadly cosmic radiation. However, this powerful barrier is not static: there have been moments in its history when the north and south magnetic poles have changed places, weakening the magnetic shield.
What is the Earth’s magnetic field?
The Earth’s magnetic field, or geomagnetic field, is a complex and dynamic phenomenon that extends from the bowels of the planet far into space. According to the theory, the field is generated in the liquid outer core of the Earth during a process called geodynamo. In this system, a rotating and electrically conductive fluid is able to maintain a magnetic field for a very long time.
Three main conditions are necessary for the operation of a dynamo:
· An electrically conductive liquid medium. In the case of the Earth, it is molten iron in its outer core.
· Kinetic energy from the rotation of the planet. The rotation of the Earth creates vortices of molten metal inside it. These vortices generate electric currents that support the magnetic field.
· Internal energy source. The heat coming from the inner core and the process of its gradual solidification provide energy for these processes.
The magnetic field plays a vital role in protecting the planet. It deflects most of the charged particles of the solar wind and cosmic rays. Without this shield, called the magnetosphere, the constant bombardment by the solar wind would destroy the upper layers of the atmosphere, including the ozone layer, which protects the surface from harmful ultraviolet radiation.
In addition, the field is important for navigation. People have been using compasses since the 11th century. Many living organisms, from bacteria to birds, whales, and sea turtles, use the magnetic field for orientation and navigation during migrations.
What is inversion?
Geomagnetic inversions are not sudden events, but long—term geological processes. They don’t happen instantly, but over thousands of years. The duration of a complete inversion can take from 2 to 12 thousand years.
The process itself usually includes three stages:
· Reduced intensity. The strength of the magnetic field drops significantly by 90% of the norm.
· Multipolarity. The field is becoming more complex, and more than two poles may temporarily exist on the planet.
· The final inversion. The magnetic field regains its strength and aligns in the opposite direction.
Currently, the strength of the Earth’s magnetic field is decreasing: over the past 3,000 years, it has lost 30% of its intensity, and since the 1830s – 10%. Some scientists consider this to be a sign of an approaching inversion. However, it is extremely difficult to predict when exactly the next complete inversion will occur.
The researchers obtained key evidence by studying the expansion of the seabed. As new oceanic crust forms on the mid-oceanic ridges, the cooling lava records the polarity of the magnetic field. This creates characteristic “bands” of alternating polarity on both sides of the ridges.
By studying these records, scientists have established that the last complete inversion, known as Brunes-Matuyama, occurred about 780,000 years ago. But there have also been incredibly long periods of stability in Earth’s history, such as the Cretaceous normal superchron, which lasted for about 37 million years without a single inversion.
Geomagnetic inversions are natural processes that do not cause catastrophic geological events. There is no scientific evidence linking them to earthquakes, volcanic eruptions, or shifting of the Earth’s axis of rotation. Earthquakes are caused by the movement of tectonic plates, a process independent of the magnetic field.
The Earth’s biosphere has successfully survived hundreds of such events. There is no evidence to suggest a link between mass extinctions and inversions. Even during periods of weakening of the magnetic field, the Earth’s atmosphere provides protection from radiation on the surface. Thus, there is no direct catastrophic threat to human life from inversion.
Threats to humans and animals
Although the threat to life on the surface is minimal, a modern society dependent on technology will face serious problems when inverted. During the inversion, the strength of the magnetic field on the surface can weaken by 90%. This means that a much larger stream of solar and cosmic radiation will reach the Earth’s atmosphere and possibly its surface.
A good example of a weakened field is the South Atlantic Anomaly, a vast area where the field is now about three times weaker than at the poles. Satellites flying through it are constantly experiencing failures due to increased radiation. This anomaly may serve as a harbinger of what will happen on a global scale during the inversion.
Modern technologies are vulnerable to the enhanced effects of space weather with a weakened magnetic field. Here are some examples:
· Satellites. Devices that provide GPS, communications, and weather forecasts are sensitive to radiation damage, which can lead to disruptions in navigation and communication.
· The power supply may be damaged. For example, in 1989, there was an accident in Quebec, when 6 million people were left without electricity for 9 hours due to a geomagnetic storm.
· Other infrastructure is also at risk, such as railway systems.
Although the atmosphere protects the surface well, during the inversion, some people will receive a large dose of radiation. For humans on earth, the average annual radiation exposure during inversion will increase slightly.
However, for astronauts, especially outside of low Earth orbit, radiation doses from solar particles can become “potentially fatal.” Passengers and aircraft crews on high-altitude flights, especially on polar routes, will also face increased exposure.
Many migratory animals rely on magnetoreception for navigation, and inversion can disrupt this ability. Birds, whales, sea turtles, and even bees have a sense that allows them to detect the Earth’s magnetic field. They use it to determine their direction and their location.
A weakened or shifting field can disrupt these navigational abilities. For example, solar storms that distort the field are associated with beaching of whales, which suggests a violation of their magnetoreception. Although animals have survived past inversions, scientists have no consensus on how they will cope with the future.
Geomagnetic inversion is a natural and repetitive process that has not led to global catastrophes or mass extinctions in the past. However, this ancient natural process poses a new serious threat to modern technology-dependent society.
The main risks are associated with the weakening of the magnetic shield, which can lead to the failure of satellites, disruption of GPS, communications and large-scale power outages. But if you are not going to leave Earth in the near future, changing the magnetic poles of the planet does not pose any risks for you.
By Nikita Shevtsev
