Electromagnetic Pulse: Characteristics, Types, Range and Wave Form

Electromagnetic Pulse (EMP), also called transient electromagnetic disturbance, can be defined as electromagnetic radiation that results from the secondary reactions that take place when nuclear gamma reactions have been absorbed by air or ground. An electromagnetic pulse is a type of electromagnetic wave and is similar to that of radio waves. An electromagnetic pulse can occur under two circumstances which are, the explosion of a nuclear weapon above the earth’s surface or a huge solar flare. 

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Key Terms: Electromagnetic pulse, pulse, natural EMP, range of frequencies of Electromagnetic Pulse, frequency range.

Electromagnetic Pulse

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In simpler terms, Electromagnetic Pulse is an intense burst of electromagnetic energy caused by any nuclear explosion in the atmosphere. It has a range of potential frequencies, shape, amplitude and duration. Its effects are severe and are capable of causing much damage to the power lines, electronic equipment, telecommunication, etc. However, there is no evidence of an EMP causing any kind of physical threat to human life. 

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Pulse Definition

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In terms of physics, a pulse can be defined as a single disturbance or vibration that moves from a given point to another through a medium including a vacuum. The amplitude of a pulse is a measure of how far the medium in which the pulse is traversing is displaced from its mean position and the length of the pulse tells how long the pulse is.

Functional Electrical Stimulation Parameters

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Characteristics of Electromagnetic Pulse

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1. Electromagnetic Pulse (EMP) is an explosion of electromagnetic radiation.
2. It can occur naturally as well as be made by humans.
3. Low to high frequency pulse is present.
4. An EMP weapon is capable of creating a pulse that can create a robust electromagnetic field.
5. It occurs in the Sun and other stars at short intervals.
6. It is just one pulse of energy that vanishes entirely in a fraction of seconds.
7. Attackers who plan to cause grave damage detonate EMP weapons at high altitudes.

Also read: Pulse Amplitude Modulation

Types of Electromagnetic Pulse

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Electromagnetic pulses can be broadly classified into 3 main categories that are:

1. Natural
2. Man-made
3. Weapon effect (Military EMP)

Natural EMP:

1. Electrostatic discharge: It happens when energy flows suddenly from one charged body to another when they come close or come in contact with each other. 
2. Meteoric Electromagnetic Pulse: It happens when the meteoroid either breaks up while passing through the earth’s atmosphere or when it suddenly clashes with any spacecraft.
3. Lightning Electromagnetic Pulse: It causes large flow of current in the form of discharge.
4. Coronal Mass Ejection: These are huge eruptions of magnetized and energetic plasma from the corona of the Sun. It causes radio and magnetic disturbances on Earth. 

Coronal Mass Ejection

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Man-made EMP:

1. Frequent rushes in the power lines.
2. The electrical circuitry is being switched off.
3. The ignition systems of gasoline engines result in the creation of pulses when their spark plugs are energized or fired.

Military EMP:

1. Nuclear Explosion: It results in the formation of a nuclear electromagnetic pulse that is put to use during wars and also to make bomb-like weapons.
2. Non-nuclear explosion: It results in the formation of non-nuclear electromagnetic pulses. These explosions are not nuclear in nature.

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Range of Electromagnetic Pulse

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A range of frequencies of Electromagnetic Pulse can be observed. Some pulses can be seen with very low frequencies while others can be seen with very high frequencies. The frequency depends on the source of the Electromagnetic Pulse. 

The range can be defined as EMP which can also be implied as DC to the daylight. However, it excludes the higher frequency ranges which are the ionizing and optical ranges.

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The Waveform of Electromagnetic Pulse

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A waveform is a curve that depicts the shape of the wave or pulse. It describes the way the instantaneous amplitude alters with time. EMP traverses in a way in which it builds up and reaches its maximum level quickly. 

Rectangular Pulses:

They are the pulses that emerge from a controlled switching circuit that have a rectangular/square shape.

Rectangular Pulse

Double Exponential Pulses

They are the ones that go up steeply and reach the peak, then come back down slowly. 

Double Exponential Pulse

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Damped Sine Wave Pulses

They are the ones that have lower energy and a narrow frequency range. 

Damped Sine Wave Pulse

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Things to Remember

1. Electromagnetic pulse (EMP) is essentially electromagnetic radiation that results from a nuclear explosion.
2. EMP is capable of damaging electronic devices temporarily as well as permanently by giving rise to high levels of voltage and current. It can also result in the device being blown apart.
3. Characteristics of EMP vary greatly with the height with which it is released.
4. An EMP attack can cause harm to even the entire country at once. 
5. A metal box called Faraday Cage has been curated to protect the items that are kept inside it from any sort of EMP attack.

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