How Strong is the Earth's Magnetic Field?

Michael Anissimov
Michael Anissimov

The Earth's magnetic field varies depending on your location on the Earth's surface. In regions near the magnetic poles, such as Siberia, Canada, and Antarctica, it can exceed 60 microteslas (0.6 gauss), whereas in regions farther away, such as South America and South Africa, is around 30 microteslas (0.3 gauss). Near the poles, the field strength diminishes with the inverse square of the distance, whereas at greater distances, such as in outer space, it diminishes with the cube of the distance. Where the prime meridian intersects with the equator, the field strength is about 31 microteslas.

The Earth's magnetic field is strongest near the magnetic poles, such as in Siberia.
The Earth's magnetic field is strongest near the magnetic poles, such as in Siberia.

The region where the Earth's magnetic field lines extend into space is called the magnetosphere, and influences the trajectories of the charged solar wind at distances exceeding 10 Earth radii. Solar wind, ejected from the Sun in all directions at great speeds, collides with the magnetosphere in a region called the bow shock. Like gravity, magnetism has an infinite range, although it diminishes so quickly with distance that its power at ranges much beyond 10 Earth radii is very low.

A horseshoe magnet is about twice the strength of a bar magnet, which is much stronger than the Earth's magnetic field.
A horseshoe magnet is about twice the strength of a bar magnet, which is much stronger than the Earth's magnetic field.

30-60 microteslas for the magnetic field of the Earth may not sound like a lot, but when you take into account the total volume of the field, its total energy is extremely large, much larger than any magnetic field generated artificially. To get a better idea for what a tesla is, a typical bar magnet has a field strength of 10 milliteslas, a strong electromagnet 1 tesla, a strong lab magnet 10 teslas, and the surface of a neutron star, about 100 megateslas.

The Earth has a planetary magnetic field.
The Earth has a planetary magnetic field.

The Earth's magnetic field may not be so strong in comparison to localized magnetic fields, but it does effect minerals all over the surface of the Earth. When magma leaks out of cracks in the oceans and cools, the Earth's magnetic field orientation is reflected in the resulting structure of the cooled rock. By analyzing magma that hardened millions of years ago, scientists have found that this field flips every 250,000 years or so.

Antarctica has a relatively strong magnetic field.
Antarctica has a relatively strong magnetic field.
Analyzing hardened magma allowed researchers to determine the magnetic field flips every 250,000 years.
Analyzing hardened magma allowed researchers to determine the magnetic field flips every 250,000 years.
Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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Discussion Comments


So what is the value of the earth's magnetic field at the equator? And how many times it is to the value of earth's magnetic field at the poles?


To answer the article's question, the strength of earth's magnetic field is huge. It's too strong for any human intervention to impact.

@turquoise-- Yea, that argument has been going on for a while. It was on a couple of TV programs too and they also gave the hole in the magnetic field roughly located in South Atlantic as evidence of a polar shift being underway.

But really we have no proof if the polar shift has started or how long it's going to take. And if it did, how long we would be left "without" a magnetic field when the shift occurs.

So we don't need to get all worked up and start freaking out just yet. But if people want to know theoretically what would happen, it would mess up a lot of things. Including weather, animal and human life (like migration). It might affect satellites and will definitely affect electronics. One thing is for sure, a compass would become pretty useless.


@simrin-- No, we don't know why it's weakening or what the result will be. But there are theories that when the earth's magnetic field becomes low enough, the poles will flip. What this means is that the North Pole will become the South Pole and vice versa.

Just because the magnetic field is weakening pretty rapidly now doesn't mean that this is going to happen soon. Some scientists think that it's going to happen in the next thousand years, but really it's probably going to be way longer than that. It could be another couple of thousand years until it happens.

The weakening of the magnetic field is not like a count-down. It can start but stall anywhere in between. Scientists know that this has happened before in earth's history.

I'm not sure what this changing magnetic field will mean for life on earth but it will definitely make us more susceptible to solar activity until the magnetic field builds up to strength again.


@anon28804-- I've also heard that there are changes happening in regards to the strength of the earth's magnetic field. If it's true that the strength decreased by 10% in the past 150 years like @anon63285 said, what's going to happen if it continues like this?

Is it possible for the earth to lose it's magnetic field altogether? If that happens, would it be disastrous for us in terms of weather and natural disasters?

I can't even imagine what the earth would face in that situation. And do we know what's causing the earth's magnetic field intensity to get weaker?


@anon97582: Yes, it could be made, and they are being tested in the laboratories, however at the moment (2010) too heavy to be used in spacecrafts, so this requires a new technology which would help minimize the weight of the magnetic field generator. Hopefully it will come out soon.


Would it be possible to create a man made magnetosphere to protect a spacecraft from radiation?


i want to know why the earth has such a large magnetic field!


decreased by 10 percent over 150 years.


Has the Earth's magnetic field strength been constant in the 100 years or so that it's been measured or has it increased/diminished?

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