The flipping of the planet's magnetic pole sounds like the plot of a disaster movie, but it seems to happen cyclically and at somewhat predictable intervals. In fact, for the past 20 million years or so, Earth’s magnetic field has flipped every 200,000 to 300,000 years — although it seems that it has been more than twice that long since the last one.
But what does this mean? Could the next geomagnetic reversal occur at any time? And if that is the case, should we be worried?
What is Earth’s magnetic field?
The Earth’s magnetic field is a magnetic field that originates in its core. The reason why Earth has a magnetic field is due to its solid iron core that is surrounded by an ocean of hot, liquid metal, which generates an electric current as it moves.
The molten, conductive fluid in the Earth is constantly moving. Earth’s core is extremely hot, over 9,000°F (5,000°C), even hotter than the outer layer of the Sun, and this heat drives convection currents in the outer core. The constant movement of the molten outer core around the solid iron inner core generates a magnetic field via the dynamo effect, which extends out into the space around the Earth.
The magnetic field shields the planet from the effects of the solar wind, and this is what allows life on Earth to exist.
The solar wind is full of charged particles, magnetic clouds, and radiation which would severely damage any life that might exist. Earth's magnetic field, or magnetosphere, serves as a shield, deflecting and redirecting the solar wind.
In fact, when the solar wind slams into the magnetosphere, it produces the aurora borealis, the northern and southern lights in the polar regions. When charged particles from the sun strike atoms in Earth’s atmosphere, electrons move to higher-energy orbits. When the electrons move back to a lower-energy orbit, it releases a particle of light or photon.
The Earth’s magnetic field went on to create the magnetic poles, which are located near the geographical poles but not exactly “on” them. For example, in 2015, the geomagnetic North pole was situated on Ellesmere Island, Canada, while the geographical North pole remained at the “center” of the globe, about 310 miles (500 kilometers) apart.
This is because the geographical poles don’t really move over time, but geomagnetic poles do. The Earth’s magnetic field is not 100% stable and due to variations in the strength of the field, the poles can migrate until they eventually “trade places” — the North pole becomes the South pole and vice versa. This is what’s called a magnetic reversal, and according to some sources, the process can last up to 28,000 years.
The effects of geomagnetic reversal
The last flip of Earth’s magnetic poles, according to some research, may have occurred around 42,000 years ago and seems to have been accompanied by a weakening in the magnetic field, which is believed to have caused a global environmental crisis towards the end of the Glacial Period. This short magnetic reversal is known as the Laschamp excursion because the first evidence of the event was discovered in the Laschamp lava flows, French Massif Central, in the 1960s.
The ozone layer damage caused by the severe weakening of the Earth's magnetic field during the Laschamp event may have led to drastic changes in weather patterns. These changes may, in turn, have led to the extinction of the most megafauna species and perhaps even the Neanderthals.
However, other instances of the flipping of the magnetic field do not seem to have been accompanied by any drastic changes in plant or animal life. In fact, given the frequency with which the field has flipped over time (estimated to be at least hundreds of times over the past three billion years), the event is unlikely to have affected the ability of life to exist on Earth.
During the Laschamp excursion, the North Pole wandered across North America and then rapidly down through the Pacific to Antarctica. The North Pole remained in Antarctica for around 400 years and then rapidly moved back up through the Indian Ocean to the North Pole. However, these changes were accompanied by a weakening in the magnetic field to as low as about six percent of its strength today.
The ozone layer was very damaged and living beings were exposed to the harmful ultraviolet light more directly than ever. Extreme climate changes and natural disasters are also believed to have occurred during this period.
As frightening as it sounds, many scientists believe that this doomsday scenario is extremely exceptional. While nobody can ensure that something like this won’t happen again in the history of Earth, when the magnetic reversals take place over thousands of years, as they almost always do, the effects on Earth are less dramatic.
But, as NASA points out, the Earth's magnetic field weakens and strengthens all the time, but there is no indication that it has ever disappeared completely. A weaker field would certainly lead to an increase in solar radiation on Earth but Earth's thick atmosphere also offers protection against the solar wind. The field would have to weaken considerably, as during the Laschamps excursion, to have such a devastating effect. In this case, we’d be at higher risk of developing cancer, because of the higher amount of radiation entering the Earth.
According to space researcher Daniel Baker, some parts of the planet could become uninhabitable due to radiation. In terms of human health, cancer is not the only side effect of unfiltered radiation. There are also several degrees of radiation poisoning and radiation-induced mutations that could cause other diseases.
Furthermore, the navigation systems based on the Earth’s magnetic field would need to be recalibrated or those relying on them would get lost. Compasses, airplanes, and migratory animals would all become disoriented while the magnetic field realigns. If the realignment occurred slowly, they might have time to adapt. If there were a sudden realignment, this could lead to mass extinctions.
It is also known that a weaker magnetic field could affect power grids and communications. Currently, satellites and spacecraft have issues when they pass through the South Atlantic Anomaly (SAA), an area between South America and South Africa in which the Earth’s magnetic field is weaker than anywhere else on the planet.
Although some people think that the SAA evidences an incoming magnetic flip, scientists haven’t really been able to predict when the next one will happen because magnetometer records indicate that the Earth’s magnetic field can suffer from severe intensity fluctuations without them resulting in a reversal.
The Sun flips its magnetic field, too
One of the most important pieces of evidence of rotation affecting the magnetic fields of celestial bodies is in the sun. The sun’s rotation produces magnetic field reversals every 11 years.
In 2017, researchers from the University of Montréal, the Harvard-Smithsonian Center for Astrophysics, the Universidade Federal do Rio Grande do Norte, and others created 3D simulations of several stars to confirm the relationship between the rotation and magnetic field reversals.
They concluded that the slower a star rotates, the quicker its magnetic cycle repeats itself. And while Earth rotates every 24 hours, the sun rotates at the equator every 25 days and even longer at higher latitudes. This is why the Sun’s magnetic cycle is extremely short in comparison to the Earth.
The movements of the sun's magnetic field near sunspots cause solar flares —explosions that often release coronal mass ejections (CMEs). These are eruptions that can produce geomagnetic storms in the Earth's magnetosphere, affecting the Earth's magnetic field and therefore, crippling power grids and interfering in communications, to say the least.
Depending on the magnitude of the event, the effects on Earth could be even more intense. For example, Daniel Baker of the University of Colorado noted in 2014 that if the 2012 solar superstorm had hit the Earth, "we would still be picking up the pieces", with massive radio and power blackouts and GPS navigation malfunctions.