Earth’s Magnetic Field and Magnetic Elements

Introduction

The Earth’s magnetic field and magnetic elements are free-floating magnetic needles that come to rest roughly along the geographical north-south axis of the Earth. This demonstrates that the Earth works as a massive magnetic dipole, with magnetic poles located at its poles.

Because the magnetic needle’s north pole will come to rest pointing at the geographic north (NG) of the Earth, the magnetic pole near the geographic north is called the Earth’s magnetic south pole (Sm). Similarly, the pole near the geographic south of the Earth is the Earth’s magnetic north pole (Nm).

The Earth’s magnetic field and magnetic elements can be defined entirely in specific quantities called the magnetic elements of the Earth. These quantities are:

• The magnetic variation, also known as declination.

• Dip or inclination, denoted by δ.

• The horizontal component of the Earth’s magnetic field, represented by Bh.

Magnetic Fields

The Earth’s magnetic field is similar to that of a bar magnet that has been inclined 11 degrees from the Earth’s axis of rotation. The problem with this picture is that the Curie temperature of iron is around 770 C. The core of the planet is hotter and therefore not like that. Question is then, How did the Earth get its magnetic field? 

The magnitude varies over the Earth’s surface from 0.3 to 0.6 gauss. Rock samples of different ages in similar locations show different directions of permanent magnetisation. 

Although the details of the dynamo effect are not fully known, the Earth’s rotation plays a role in creating the currents believed to be the source of the magnetic field. The Mariner 2 spacecraft found that Venus has no such effect even though the planet’s main iron content should be similar to the Earth’s magnetic field. The rotation period of Venus of 243 Earth days is too slow to produce the dynamo effect.

Magnetic Susceptibility Formula

The magnetic susceptibility formula of a material, indicated by m, refers to the ratio of the magnetisation M within the material to the applied magnetic field strength H.

m=MH

According to this formula, the absolute temperature of a magnet is inversely related to paramagnetic susceptibility.

Types of Magnets

The magnet is primarily classified into three categories:

Permanent magnet: is a magnet made of a permanently magnetized substance that generates its continuous magnetic field. Magnetisable materials are also called ferromagnetic materials. Examples include materials like iron, nickel, and cobalt.

Temporary magnet: is a magnet that is only magnetized for a limited time. These magnets are often made up of soft materials with low magnetic characteristics. They become magnetized for a brief time when a solid or permanent magnet attracts them.

Electromagnet: An electromagnet is a magnet that generates a magnetic field due to a current passing through it. Wire twisted into a coil is the most common electromagnet; as current travels through the wire, a magnetic field is formed inside the coil. When the current is turned off, it goes away. Electromagnets are commonly found in motors, generators, and hard disc drives.

Basic properties of magnets:

The following are some basic properties of magnetic elements.

• When submerged in iron filings, the filings stick to the magnet’s ends. Attraction is greatest at the magnet’s two ends. The magnet’s poles are the opposite ends.
• When a magnet is suspended freely, it always points north-south. The north pole, N, is the pole that points to the geographic north, and the south pole, S, is the pole that points to the geographic south.
• Magnetic poles are always found in pairs. The isolated magnetic pole, in other words, does not exist. Because the magnet bars are positioned slightly inwards from the magnet’s free ends, its magnetic length is always shorter than its geometric length.
• Poles that are similar repel each other, while different poles attract each other. (We can detect repulsion when the North Pole of one magnet is brought near the North Pole of another magnet, but attraction when the North Pole of one magnet is drawn close to another magnet’s South Pole.)
• Coulomb’s inverse square law describes the force of attraction or repulsion between two magnetic poles. The symbol for pole strength is m, and the unit is an ampere meter.

Three elements of the Earth’s magnetic field

The size, as well as the direction of the Earth’s magnetic field, are determined by three elements of the Earth’s magnetic field:

• Magnetic declination.

• The magnetic inclination or the angle of dip.

• The horizontal component of the Earth’s magnetic field.

Magnetic Declination

Magnetic declination is the angle between the true north and the magnetic north. On the horizontal plane, true north is never in the same place and varies based on the location on the Earth’s surface and the passage of time.

Magnetic Inclination

The angle of dip is another name for the magnetic inclination. The angle is formed by the horizontal plane on the Earth’s surface. The magnetic equator has a 0° angle of dip, while the magnetic poles have a 90° angle of dip.

Causes of the Earth’s magnetism:

Some possible reasons for the Earth’s magnetism include:

• Magnetic masses in the Earth.

• Electric currents in the Earth.

• Electric currents in the upper atmosphere of the Earth.

• Radiation from the Sun.

• The presence of the moon.

The Earth’s magnetic field, on the other hand, is thought to be caused by the melted charged metallic liquid inside the Earth’s surface, which has a radius of roughly 3500 km in comparison, the Earth’s radius is 6400 kilometers.

Conclusion 

The Earth’s magnetic field is believed to play an essential role in making the planet habitable. A magnetic field not only determines the direction of our compass needles but also acts as a kind of shield that deflects the solar wind that could otherwise destroy the air as we know it – the atmosphere. Therefore, the Earth’s magnetic fields are an essential topic of study and research in physics.