Science Facts

What Happens When Earth’s Magnetic Field Reverses?

Earth Magnetic Field

Scientists claim that the earth’s magnetic poles will reverse within the next few thousand years. So why does that happen? The north and south poles weren’t always that way. About 786,000 years ago, the earth’s magnetic field reversed, and it’s remained constant ever since. But before that happened, the south was north. According to scientists, every half million years, the earth’s dipole magnetic field starts to weaken before eventually reversing completely. It’s thought to be caused by changes in the fluid portion of the earth’s iron core.

About 20 million years ago, the Earth’s magnetic field reversed about once every 200,000 to 300,000 years. This is called a geomagnetic reversal. Recent research shows that the Earth’s magnetic field is weakening at a rate ten times faster than they previously thought. It is about 5 percent per decade, a sign that the magnetic field may be starting the process of reversing. There isn’t any evidence to suggest that magnetic field reversals in the past have led to any mass extinctions.

What happens when earth’s magnetic field reverses?

The direction of the magnetic field depends on the direction of the giant electrical currents, which in turn depend on the direction of small magnetic loops. The helical convection flows generate it. If the magnetic field were switched off entirely, it would reestablish itself randomly, with the north and south magnetic poles aligned either one way or the other.

There seems to be no pattern in the geological record when the field flips, nor to which alignment is preferred. So that’s probably how the reverse happens. Earth’s magnetic field isn’t necessarily switched off. But it’s scrambled in some way. It then builds up again, choosing its direction randomly.

  • When it does a full reverse, it created a geomagnetic reversal.
  • When the field just glitches but ends up in the same direction, it started a geomagnetic excursion.

Effects on earth surface

There are a few ideas on how these glitches might happen. It may be that some event triggers a disruption in the flows within the outer core. It could be an asteroid or comet impact, an interaction between the core and mantle. Scientists presumed this reversal process took a few thousand years. But new evidence suggests that the most recent major reversal 786,000 years ago happened in less than 100 years, roughly the span of a single lifetime. Obviously, flips like this have occurred several times throughout Earth’s history.

Scientists say the next one may happen within the next few thousand years. New evidence indicates that the intensity of the Earth’s magnetic field is decreasing at a rate 10 times faster than normal. It leads many geophysicists to believe that we’re on the brink of another reversal. So what would happen if that did occur? Would there be any noticeable changes? The good news is there are no documented catastrophes associated with past reversals.

The Earth has a magnetic field for millions of years. It protects from radiation from space and coronal mass ejections from the Sun. A magnetic reversal would almost surely wreak havoc on our electrical grid. It could potentially bring it down. Also, It would make vulnerable to energetic particles from the sun and cosmic rays, both of which can cause genetic mutations. And that could happen before the reversal even takes place.

Navigational change

Our navigational equipment would get disoriented, and compasses would point to the wrong part of the world. Depending on how slowly it reverse, the blow on the animal kingdom could be much worse.

  • If it moves too fast, this could cause mass extinctions of thousands of species that rely on the magnetic field to find their migration grounds or their spawning grounds.

If the magnetic field continues to weaken, there is still an atmosphere to protect from harmful radiation. The main concern is that power grids and communications systems may be at risk. Also, any animals that use the magnetic field to navigate might be confused for a while. Research suggests that many of them rely on the magnetic field for finding their way. Birds migrate by following a certain field gradient.

Homing pigeons find their way home by using the magnetic field. And it is theorized that many migrating fish, like salmon, use the magnetic field to find their way. Some predators, like foxes, prefer to attack from a North-Eastern direction and large grazing animals tend to align north-south while grazing. Any animal that uses the magnetic field for navigation would surely get lost and probably die on the way.

There’s a period before reversals where the magnetic field gets progressively weaker. And the genetic mutations that arise from that could potentially increase cancer rates. So the longer it takes for that reversal process to complete, the more harmful it would be to us. Humanities would be to move underground and start a new civilization there, with thick layers of rock protecting us from the radiation. Going to the surface would only be possible for short whiles, and most probably a special suit would be needed.

The magnetic field has weakened by over 20% in this century at ‘South Atlantic Anomaly.’ And half of its area has grown by over 3 times to a massive 105 million square km. It equals roughly 70% of all the world’s landmass and about one-fifth of the Earth’s total surface. The magnetic field in this area is so weak that many satellites suffer problems when flying over it.

Their systems malfunction, they lose communication, some break altogether. The Hubble space telescope stops observing and shuts down sensitive equipment when flying through this zone. NASA astronauts have reported seeing many ‘shooting stars’ when passing the region, which in reality are cosmic particles hitting their retinas. It has also been reported that a flyby through this region once fried several modern laptops on the International Space Station.

If the weakening of the field in this region continues, it might become impossible to fly airplanes through it. The risk of failing electronics and a higher risk of cancer for the passengers and airplane staff. Satellites could stop working completely in this region, severely crippling their technology. If the region grows large enough, it can even influence our global network.

Currently, the anomaly is mostly above the ocean, but it is already over many South America and Africa. However, at the rate that this anomaly is growing, it will envelop the United States in roughly 100 years. And the field will have weakened by another 15%. The entire world will be enveloped in roughly 350 years, by which time the field will have only 50% of the strength of today. A small consolidation is that we would be seeing auroras at all latitudes and quite regularly. History shows that during a polar reverse, many things can happen.

  • There are also recorded cases of the magnetic poles breaking up into 4, 6, and even 8 due to instabilities in the Earth’s core.

All of these fields will be much weaker than the current one and point in random directions. The fields will be very messy and much less capable of defending themselves from the harsh conditions of space. For this reason, it is very important to study the Earth’s magnetic field and predict what will be happening.

The forerunners of this are the European Space Agency with their Swarm satellites. These spacecraft form a constellation and scan the Earth for over 6 years now, making very accurate maps of the Earth’s magnetic field. Knowing how and when the field is changing will allow us to predict the required level of protection for satellites and plan to minimize this influence on the planet.

What causes magnetic field?

Magnetic fields are generated in two ways: In magnetic materials like iron, the tiny magnetic fields of their constituent particles align to give a global field. Alternatively, flows of many charged particles like electrons can produce magnetic fields. For example, in an electromagnet. But Earth’s interior is not intrinsically magnetic. It’s too hot for the iron atoms in the core to spontaneously align.

Although the interior is rotating, it’s electrically neutral, So there shouldn’t be an overall electrical current. Beneath the thin crust and 2900 km of solid mantle lie earth’s core. The 2400 km thick outer core is molten iron and nickel, and some other stuff. Beneath this layer is the inner core, a 1200 km radius ball of solid iron. It’s solid because of the pressure at that depth at around 5500 Kelvin temperature. It would instantly melt at lower pressures.

The outer core has a rotation gradient. The outer layer rotates a bit slower than the surface. But it speeds up deeper, and that motion gets messier. As the inner core grows, it releases non-iron impurities that flow upwards, joining convection streams. These flows are then twisted into helixes by the Coriolis force, the same effect that produces hurricanes on Earth’s surface. It’s all of this motion that together produces Earth’s magnetic field through a process.

The reason that the Earth even has a magnetic field has to do with the molten iron in the outer core. The motion of that molten iron and some complicated physics generate a magnetic field through something called the dynamo effect. For reasons, the molten iron’s motion must somehow change to reverse the magnetic field. Dynamo theory not only explains geomagnetism but also why Earth’s field sometimes reverses its polarity.


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