The Magnetic Field of Earth

A self-exciting dynamo process in the fluid outer core generates the Earth’s magnetic field. The magnetic field is created by electrical currents running through the slowly moving molten iron. In addition, external sources, including but not limited to the ionosphere and magnetosphere, also contribute to the geomagnetic field observable at the Earth’s surface. There are many variations in the geomagnetic field on a range of scales, which we will now discuss across both space and time domains.

What is the Earth’s Magnetic Field?

The magnetic field surrounding the earth is also referred to as a geomagnetic field. It can be seen from millions of kilometres into outer space and looks much like a bar magnet or a piece of metal that has been placed under the magnet. The magnetic north pole is in Antarctica, while the south pole switches between two places now and then but is currently in the South Pole. 

This creates a strange phenomenon where if you’re standing over either magnetic pole, it doesn’t seem as though there is any magnetic field over them because they both attract due to how their polarity has been reversed temporarily! So you could very easily stand on one of them and nothing would happen to you, except perhaps your head would start getting dizzy when you look closely at either end.

The Earth’s Magnetism Theory

It is a theory that explains how the planet’s magnetic field works.

Dynamo Theory

For the earth to have an electromagnetic field, it needs a molten fluid to act as an electric conductor. One of these fluids is iron-rich and is located in the outer core, while another that also contains iron can be found in the inner core and remains solidified.

What causes the Earth’s magnetic field to exist?

The earth is a magnet surrounded by magnetic fields. About 99.9% of the earth’s volume comprises metals, with 0.01% being liquid iron. The rapid spinning motion of a thin inner core melts the solid impurities generating plasma at 10,000 degrees Fahrenheit! Convection current produced by heat in the earth’s core transfers electrical charge to this molten iron creating an electric current. 

This electric current creates the magnetic field around the earth, which deflects incoming solar rays that would otherwise damage our atmosphere and greenhouse gases preventing life on earth from being capable of sustaining itself. It’s a common misconception, but the earth’s magnetic poles aren’t aligned to the actual geographic north and south poles.

Places like Canada have essentially become the current magnetic North Pole, while areas like Antarctica are the new geographic North Pole. It may surprise you that though they are essentially in reverse, their inclination or distance from the Earth’s rotational axis is still 10 degrees! So your compass would still point in the direction of Canada instead of true north, even though it’s not technically accurate anymore (at least for now). Without this magnetic field, life as we know it would not be possible due to incoming charged particles from the solar wind, which could destroy our atmosphere without the protection provided by its natural magnetism.

Representation Of Earth’s Magnetic Field

Anywhere you go on Earth, a three-dimensional vector represents the magnetic field. A typical procedure for measuring its direction involves using a compass; the direction of the needle determines what we mean by magnetic North. 

The difference between it and true north is known as declination (D) or variation. Facing magnetic North, if the compass reads an angle relative to horizontal, this is inclination (I). The intensity (F) of the field depends on how strong it is in response to lifting iron objects.

1. Declination

• Declination is a positive angle for an eastward deviation of the field relative to the true north. It may be calculated by comparing the direction of a celestial pole to the magnetic north-south heading of a compass.
• For example, maps usually show the declination diagrammatically through closely spaced parallel lines in some countries. Each line represents one degree of difference between magnetic north and true (geographic) north for that portion of the map. 
• A separate declination diagram might also show calculated values for cities and prominent places.

2. Inclination

• The inclination is given by an angle that might take on a value between -90° (heading upwards) and 90° (- pointing straight down).
•  In the northern hemisphere, the field points in a downward direction. It is straight down at the magnetic north pole and continues to rotate upwards as one moves towards lower latitudes until it levels out horizontally at the magnetic equator. 
• As latitude decreases with increasing southern travels, inclination also tilts downwards until it’s straight up in the southern hemisphere at the South Magnetic Pole.

3. Intensity

• The intensity of the field (also known as magnetism) is often measured in gauss (G), with 1 G = 100 μT. 
• Scientists can measure the Earth’s magnetic field and send the data out to a satellite, which sends it back so that it can be analysed. On average, the Earth’s magnetic field ranges between 0.25 and 0.65 G. 
• This is measured using something called a ‘geomagnetic dipole’. 
• Compared to a powerful refrigerator magnet with a field of about 10,000 μT (1000 Gauss), this level falls well short. However, for some animals, it is still extremely challenging because of its impact on them due to their smaller size and non-symmetrical shape.

Conclusion

In this article, we have discussed what Earth’s magnetic field is. The magnetic field surrounding the earth is also referred to as a geomagnetic field. We also learned about the Earth’s Magnetism Theory which explains how the planet’s magnetic field works and also we learned about Dynamo Theory. We also talked about the source of Earth’s Magnetic field. In the end, we discussed the representation of the Earth’s Magnetic Field, which consists of (i) The difference between it and true north is, known as declination (D) or variation, (ii) Facing magnetic North, if the compass reads an angle relative to horizontal, this is inclination (I), and (iii) The intensity (F) of the field depends on how strong it is in response to lifting iron objects.