The Earth’s Magnetism

Introduction 

The Earth has a massive magnetic field suspended surrounding it. The Earth’s magnetic field may surprise you a lot but it’s a fact that no one can deny. This can be proved easily by using a compass that can be found anywhere in the market or you can simply use the compass present in your phone. You’ll observe that the compass always points towards the North direction regardless of the direction you turn towards. 

This proves how our Earth generates a magnetic field around it. You’ll be shocked to know that the Earth’s magnetic field spans over several thousand kilometers into space. Our Earth’s magnetic field has the North Pole located in Antarctica. On the other hand, the magnetic South pole is located at the North Pole. 

The Theory of Earth’s Magnetism 

As astounding as it may sound, our Earth’s magnetic field came into existence by many theories. Some of them are:

• The Dynamo Effect 

Due to the presence of metallic fluids on the Earth’s surface, magnetism is present on Earth. The outer and inner core of Earth has molten iron and solidified materials respectively. This theory has not been confirmed but some believe it to be true. 

• The Ionization of Outer Layers 

This theory asserts that the Earth’s magnetic field is a result of its rotation on its axis. It says that the rotation produces a strong current by the ionization of the outer layers. However, the magnetic field produced by the same will be very weak. 

You may be shocked to know these theories but they also prove: Why does Earth have a magnetic field? Out of these two theories, the Dynamo Effect is more widely accepted to prove why Earth has a magnetic field? 

What are Magnetic Poles? 

The Earth’s magnetic field is generated by the presence of molten minerals like iron and nickel on its core. They have currents that aid in providing magnetic fields. These charged particles or currents keep the solar wind away from the Earth’s atmosphere. If it wasn’t for these currents, life would not exist on Earth. Solar winds are ionized particles from the sun. 

Now, if we talk about what are the magnetic poles we can simply answer by saying that the geographical North and South poles on Earth are not aligned to the magnetic North and South poles. The magnetic South pole is located in Canada. The magnetic North Pole is in Antarctica. They are aligned to almost 10° to the Earth’s axis of rotation. That tells you what the magnetic poles of Earth are like. 

When the compass is actually near these points, they stop functioning completely. 

Components of Earth’s Magnetic Field 

Three components define the magnitude as well as the direction of the Earth’s magnetic field. They are as follows: 

• Magnetic Declination 

It is defined as the angle formed between the magnetic north and true north. Since the true north may vary on the horizontal plane due to the Earth’s surface and time, the angle of declination may change constantly. 

• Magnetic Inclination 

It is also called the angle of dip. This angle is formed on the horizontal plane of Earth. At the equator, it is 0° and it is 90° at the equator. 

• Horizontal Component of the Earth’s Magnetic Field

This is further divided into two different components: 

1. Vertical Component (v) 
2. Horizontal Component (H)

However, these components can change due to numerous factors. Let’s discuss some of them. 

Variations in Earth’s Magnetic Field 

The variations in the Earth’s magnetic field are caused by:

• Lunar Variations 

The moon influences the variations in the Earth’s Magnetism. During a lunar eclipse, the tidal waves of the Earth can cause variations in the Earth’s ionized layer. This in turn can influence the magnetic field of Earth. 

• Secular Variations 

Several variations can occur in the Earth’s magnetic field due to the periodic change in the Earth’s axis. It moves from east to west. However, this takes place once in 960 years. 

• Daily and Annual Variations 

The Earth’s atmosphere is ionized by the sun’s ultraviolet rays. Due to this, the current is produced. The current results in a magnetic further. This change occurs every day and every year. 

• Eleven-Year Sunspot Cycle

The phenomenon of sunspot takes place every eleven years. The sunspot is a region of a strong magnetic field. Hence, it causes a lot of variations in the Earth’s magnetic field.

• Irregular Variations

 The sun may become very active during a particular period and show variations in the magnetic field. This may occur due to its ultraviolet rays ionizing the atmosphere. This in turn affects the magnetic field of Earth. 

Solved Example:

6. The magnetic field of Earth at the equator is approximately 4 × 10-5 T. The Earth’s radius is 6.4 × 106 m. Now, calculate the dipole moment of Earth. 

Ans. The magnetic field of Earth at the equator is approximately 4 × 10-5 T. This means, 

Dipole moment, d = 2mr 

Here, Magnetic Field, B =  μom/4πr2

d =  B × 4πr2/μo × 2 × r 

 d  = 2100 × 1020 

d = 2.1× 1023 Am2

Conclusion 

Although it is quite difficult to believe that the Earth’s magnetic field is all around the planet, it does influence a lot of phenomena on Earth and vice-versa. Due to the presence of a magnetic field around Earth, the compass always points towards the North. Moreover, the magnetic and geographical North and South poles of Earth are at opposite ends of each other. This may get you confused but we’ve tried to cover all the aspects in our article so that all the concepts are clear to you. The Earth’s magnetism can serve as one of the important concepts of class 12 Physics. Many questions are asked from this particular concept for your competitive examinations.