EMP - Electro Magnetic Pulse
"The Dreaded Blast "
An electromagnetic pulse (sometimes abbreviated EMP) is a burst of electromagnetic radiation that
results from an explosion (usually from the detonation of a nuclear weapon) and/or a suddenly
fluctuating magnetic field. The resulting rapidly changing electric fields or magnetic fields may couple
with electrical/electronic systems to produce damaging current and voltage surges.

In military terminology, a nuclear bomb detonated hundreds of kilometers above the Earth's surface is
known as a high-altitude electromagnetic pulse (HEMP) device. Effects of a HEMP device depend on a
very large number of factors, including the altitude of the detonation, energy yield, gamma ray output,
interactions with the Earth's magnetic field, and electromagnetic shielding of targets.

The case of a nuclear electromagnetic pulse differs from other kinds of electromagnetic pulse (EMP) in
being a complex electromagnetic multi-pulse. The complex multi-pulse is usually described in terms of
three components, and these three components have been defined as such by the international
standards commission called the International Electrotechnical Commission (IEC).[16]

The three components of nuclear EMP, as defined by the IEC, are called E1, E2 and E3.

E1

The E1 pulse is the very fast component of nuclear EMP. The E1 component is a very brief but intense
electromagnetic field that can quickly induce very high voltages in electrical conductors. The E1
component causes most of its damage by causing electrical breakdown voltages to be exceeded. E1 is
the component that can destroy computers and communications equipment and it changes too fast for
ordinary lightning protectors to provide effective protection against it.

The mechanism for a 400 km high altitude burst EMP: gamma rays hit the atmosphere between 20–40 km
altitude, ejecting electrons which are then deflected sideways by the Earth's magnetic field. This makes
the electrons radiate EMP over a massive area. Because of the curvature and downward tilt of Earth's
magnetic field over the USA, the maximum EMP occurs south of the detonation and the minimum occurs
to the north.[17]
The E1 component is produced when gamma radiation from the nuclear detonation knocks electrons
out of the atoms in the upper atmosphere. The electrons begin to travel in a generally downward
direction at relativistic speeds (more than 90 percent of the speed of light). In the absence of a
magnetic field, this would produce a large pulse of electric current vertically in the upper atmosphere
over the entire affected area. The Earth's magnetic field acts on these electrons to change the
direction of electron flow to a right angle to the geomagnetic field. This interaction of the Earth's
magnetic field and the downward electron flow produces a very large, but very brief, electromagnetic
pulse over the affected area.[18]

Physicist Conrad Longmire has given numerical values for a typical case of the E1 pulse produced by a
second generation nuclear weapon such as those used in high altitude tests of Operation Fishbowl in
1962. According to him, the typical gamma rays given off by the weapon have an energy of about 2 MeV
(million electron volts). When these gamma rays collide with atoms in the mid-stratosphere, the gamma
rays knock out electrons. This is known as the Compton effect, and the resulting electrons produce an
electric current that is known as the Compton current. The gamma rays transfer about half of their
energy to the electrons, so these initial electrons have an energy of about 1 MeV. This causes the
electrons to begin to travel in a generally downward direction at about 94 percent of the speed of light.
Relativistic effects cause the mass of these high energy electrons to increase to about 3 times their
normal rest mass.[18]

If there were no geomagnetic field and no additional atoms in the lower atmosphere for additional
collisions, the electrons would continue to travel downward with an average current density in the
stratosphere of about 48 amperes per square metre.[18]

Because of the downward tilt of the Earth's magnetic field at high latitudes, the area of peak field
strength is a U-shaped region to the equatorial side of the nuclear detonation. As shown in the diagram
at the right, for nuclear detonations over the continental United States, this U-shaped region is south
of the detonation point. Near the equator, where the Earth's magnetic field is more nearly horizontal,
the E1 field strength is more nearly symmetrical around the burst location.

The Earth's magnetic field quickly deflects the electrons at right angles to the geomagnetic field, and
the extent of the deflection depends upon the strength of the magnetic field. At geomagnetic field
strengths typical of the central United States, central Europe or Australia, these initial electrons spiral
around the magnetic field lines in a circle with a typical radius of about 85 metres (about 280 feet).
These initial electrons are stopped by collisions with other air molecules at a average distance of about
170 metres (a little less than 580 feet). This means that most of the electrons are stopped by collisions
with air molecules before they can complete one full circle of its spiral around the Earth's magnetic
field lines.[18]

This interaction of the very rapidly moving negatively charged electrons with the magnetic field
radiates a pulse of electromagnetic energy. The pulse typically rises to its peak value in about 5
nanoseconds. The magnitude of this pulse typically decays to half of its peak value within 200
nanoseconds. (By the IEC definition, this E1 pulse is ended at one microsecond (1000 nanoseconds)
after it begins.) This process occurs simultaneously with about 1025 other electrons.[18]

There are a number of secondary collisions which cause the subsequent electrons to lose energy
before they reach ground level. The electrons generated by these subsequent collisions have such
reduced energy that they do not contribute significantly to the E1 pulse.[18]

These 2 MeV gamma rays will normally produce an E1 pulse near ground level at moderately high
latitudes that peaks at about 50,000 volts per metre. This is a peak power density of 6.6 megawatts per
square metre.

The process of the gamma rays knocking electrons out of the atoms in the mid-stratosphere causes
this region of the atmosphere to become an electrical conductor due to ionization, a process which
blocks the production of further electromagnetic signals and causes the field strength to saturate at
about 50,000 volts per metre. The strength of the E1 pulse depends upon the number and intensity of
the gamma rays produced by the weapon and upon the rapidity of the gamma ray burst from the
weapon. The strength of the E1 pulse is also somewhat dependent upon the altitude of the detonation.

There are reports of "super-EMP" nuclear weapons that are able to overcome the 50,000 volt per metre
limit by the very nearly instantaneous release of a burst of gamma radiation of much higher energy
levels than are known to be produced by second generation nuclear weapons. The reality and possible
construction details of these weapons are classified, and therefore cannot be confirmed by scientists
in the open scientific literature.[19]

E2

The E2 component is generated by scattered gamma rays and inelastic gammas produced by weapon
neutrons. This E2 component is an "intermediate time" pulse that, by the IEC definition, lasts from
about 1 microsecond to 1 second after the beginning of the electromagnetic pulse. The E2 component
of the pulse has many similarities to the electromagnetic pulses produced by lightning, although the
electromagnetic pulse induced by a nearby lightning strike may be considerably larger than the E2
component of a nuclear EMP. Because of the similarities to lightning-caused pulses and the
widespread use of lightning protection technology, the E2 pulse is generally considered to be the
easiest to protect against.

According to the United States EMP Commission, the main potential problem with the E2 component is
the fact that it immediately follows the E1 component, which may have damaged the devices that would
normally protect against E2.

According to the EMP Commission Executive Report of 2004, "In general, it would not be an issue for
critical infrastructure systems since they have existing protective measures for defense against
occasional lightning strikes. The most significant risk is synergistic, because the E2 component follows
a small fraction of a second after the first component's insult, which has the ability to impair or destroy
many protective and control features. The energy associated with the second component thus may be
allowed to pass into and damage systems."[20]

E3

The E3 component is very different from the other two major components of nuclear EMP. The E3
component of the pulse is a very slow pulse, lasting tens to hundreds of seconds, that is caused by the
nuclear detonation heaving the Earth's magnetic field out of the way, followed by the restoration of the
magnetic field to its natural place. The E3 component has similarities to a geomagnetic storm caused by
a very severe solar flare.[21][22] Like a geomagnetic storm, E3 can produce geomagnetically induced
currents in long electrical conductors, which can then damage components such as power line
transformers.[23]

Because of the similarity between solar-induced geomagnetic storms and nuclear E3, it has become
common to refer to solar-induced geomagnetic storms as "solar EMP."[24] At ground level, however,
"solar EMP" is not known to produce an E1 or E2 component.

For a more thorough description of E3 damage mechanisms, see the main article: Geomagnetically
induced current

Practical considerations for nuclear EMP

Older, vacuum tube (valve) based equipment is generally much less vulnerable to EMP than newer
solid state equipment. Soviet Cold War–era military aircraft often had avionics based on vacuum tubes
due both to limitations in Soviet solid-state capabilities and a belief that the vacuum-tube gear would
survive better.[1]

Although vacuum tubes are far more resistant to EMP than solid state devices, other components in
vacuum tube circuitry can be damaged by EMP. Vacuum tube equipment actually was damaged in 1962
nuclear EMP testing.[14]  Also, the solid state PRC-77 VHF manpackable 2-way radio survived extensive
EMP testing.[25] The earlier PRC-25, nearly identical except for a vacuum tube final amplification stage,
had been tested in EMP simulators but was not certified to remain fully functional.

Many nuclear detonations have taken place using bombs dropped by aircraft. The B-29 aircraft that
delivered the nuclear weapons at Hiroshima and Nagasaki did not lose power due to damage to their
electrical or electronic systems. This is simply because electrons (ejected from the air by gamma rays)
are stopped quickly in normal air for bursts below roughly 10 km (about 6 miles), so they do not get a
chance to be significantly deflected by the Earth's magnetic field (the deflection causes the powerful
EMP seen in high altitude bursts), thus the limited use of smaller burst altitudes for widespread EMP.
[26]

If the aircraft carrying the Hiroshima and Nagasaki bombs had been within the intense nuclear radiation
zone when the bombs exploded over those cities, then they would have suffered effects from the
charge separation (radial) EMP. But this only occurs within the severe blast radius for detonations
below about 10 km altitude.

During nuclear tests in 1962, EMP disruptions were suffered aboard KC-135 photographic aircraft flying
300 km (190 mi) from the 410 kt (1,700 TJ) Bluegill Triple Prime and 410 kt (1,700 TJ) Kingfish detonations
(48 and 95 km (30 and 59 mi) burst altitude, respectively)[27] but the vital aircraft electronics were far
less sophisticated than today and the aircraft were able to land safely.
The mechanism for a 400 km high altitude burst EMP: gamma rays hit the
atmosphere between 20–40 km altitude, ejecting electrons which are then
deflected sideways by the Earth's magnetic field. This makes the electrons radiate
EMP over a massive area. Because of the curvature and downward tilt of Earth's
magnetic field over the USA, the maximum EMP occurs south of the detonation and
the minimum occurs to the north.[
Generation of nuclear EMP
Several major factors control the effectiveness of a nuclear EMP weapon.

These are
1.The altitude of the weapon when detonated;
2.The yield and construction details of the weapon;
3.The distance from the weapon when detonated;
4.Geographical depth or intervening geographical features;
5.The local strength of the magnetic field of the Earth.

Beyond a certain altitude a nuclear weapon will not produce any EMP, as the gamma rays will have
had sufficient distance to disperse. In deep space or on worlds with no magnetic field (the moon or
Mars for example) there will be little or no EMP. This has implications for certain kinds of nuclear
rocket engines, such as Project Orion.

Weapon altitude
According to an internet primer published by the Federation of American Scientists[30]
A high-altitude nuclear detonation produces an immediate flux of gamma rays from the nuclear
reactions within the device. These photons in turn produce high energy free electrons by Compton
scattering at altitudes between (roughly) 20 and 40 km. These electrons are then trapped in the
Earth's magnetic field, giving rise to an oscillating electric current. This current is asymmetric in
general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic
pulse (EMP). Because the electrons are trapped essentially simultaneously, a very large
electromagnetic source radiates coherently. The pulse can easily span continent-sized areas, and
this radiation can affect systems on land, sea, and air. The first recorded EMP incident accompanied a
high-altitude nuclear test over the South Pacific and resulted in power system failures as far away as
Hawaii. A large device detonated at 400–500 km (250 to 312 miles) over Kansas would affect all of the
continental U.S. The signal from such an event extends to the visual horizon as seen from the burst
point.
Thus, for equipment to be affected, the weapon needs to be above the visual horizon. Because of the
nature of the pulse as a large, high powered, noisy spike, it is doubtful that there would be much
protection if the explosion were seen in the sky just below the tops of hills or mountains.

The altitude indicated above is greater than that of the International Space Station and many low
Earth orbit satellites. Large weapons could have a dramatic impact on satellite operations and
communications such as occurred during the 1962 tests. The damaging effects on orbiting satellites
are usually due to other factors besides EMP. In the Starfish Prime nuclear test, most satellite damage
was due to damage to the solar panels from satellites passing through radiation belts created by the
high altitude nuclear explosion.[31]

















How the area affected depends on the burst altitude.

How the peak EMP on the ground varies with the weapon yield and burst altitude. The yield here is
the prompt gamma ray output measured in kilotons. This varies from 0.115–0.5% of the total weapon
yield, depending on weapon design. The 1.4 Mt total yield 1962 Starfish Prime test had a gamma
output of 0.1%, hence 1.4 kt of prompt gamma rays. (The blue 'pre-ionisation' curve applies to certain
types of thermonuclear weapon, where gamma and x-rays from the primary fission stage ionise the
atmosphere and make it electrically conductive before the main pulse from the thermonuclear stage.
The pre-ionisation in some situations can literally short out part of the final EMP, by allowing a
conduction current to immediately oppose the Compton current of electrons.)[28][29]
According to an internet primer published by the Federation of American Scientists[30]
A high-altitude nuclear detonation produces an immediate flux of gamma rays from the nuclear
reactions within the device. These photons in turn produce high energy free electrons by Compton
scattering at altitudes between (roughly) 20 and 40 km. These electrons are then trapped in the
Earth's magnetic field, giving rise to an oscillating electric current. This current is asymmetric in
general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic
pulse (EMP). Because the electrons are trapped essentially simultaneously, a very large
electromagnetic source radiates coherently. The pulse can easily span continent-sized areas, and
this radiation can affect systems on land, sea, and air. The first recorded EMP incident accompanied a
high-altitude nuclear test over the South Pacific and resulted in power system failures as far away as
Hawaii. A large device detonated at 400–500 km (250 to 312 miles) over Kansas would affect all of the
continental U.S. The signal from such an event extends to the visual horizon as seen from the burst
point.
Thus, for equipment to be affected, the weapon needs to be above the visual horizon. Because of the
nature of the pulse as a large, high powered, noisy spike, it is doubtful that there would be much
protection if the explosion were seen in the sky just below the tops of hills or mountains.

The altitude indicated above is greater than that of the International Space Station and many low
Earth orbit satellites. Large weapons could have a dramatic impact on satellite operations and
communications such as occurred during the 1962 tests. The damaging effects on orbiting satellites
are usually due to other factors besides EMP. In the Starfish Prime nuclear test, most satellite damage
was due to damage to the solar panels from satellites passing through radiation belts created by the
high altitude nuclear explosion.[31]

Weapon yield

Typical nuclear weapon yields used during Cold War planning for EMP attacks were in the range of 1
to 10 megatons (4.2 to 42 PJ)[32] This is roughly 50 to 500 times the sizes of the weapons the United
States used in Japan at Hiroshima and Nagasaki. Physicists have testified at United States
Congressional hearings, however, that weapons with yields of 10 kilotons (42 TJ) or less can produce
a very large EMP.[33]

The EMP at a fixed distance from a nuclear weapon does not depend directly on the yield but at most
only increases as the square root of the yield (see the illustration to the right).  This means that
although a 10 kiloton weapon has only 0.7% of the total energy release of the 1.44-megaton Starfish
Prime test, the EMP will be at least 8% as powerful. Since the E1 component of nuclear EMP depends
on the prompt gamma ray output, which was only 0.1% of yield in Starfish Prime but can be 0.5% of
yield in pure fission weapons of low yield, a 10 kiloton bomb can easily be 5 x 8% = 40% as powerful as
the 1.44 megaton Starfish Prime at producing EMP.[27]

The total prompt gamma ray energy in a fission explosion is 3.5% of the yield, but in a 10 kiloton
detonation the high explosive around the bomb core absorbs about 85% of the prompt gamma rays,
so the output is only about 0.5% of the yield in kilotons. In the thermonuclear Starfish Prime the
fission yield was less than 100% to begin with, and then the thicker outer casing absorbed about 95%
of the prompt gamma rays from the pusher around the fusion stage. Thermonuclear weapons are also
less efficient at producing EMP because the first stage can pre-ionize the air[27] which becomes
conductive and hence rapidly shorts out the electron Compton currents generated by the final, larger
yield thermonuclear stage. Hence, small pure fission weapons with thin cases are far more efficient at
causing EMP than most megaton bombs.

This analysis, however, only applies to the fast E1 and E2 components of nuclear EMP. The
geomagnetic storm-like E3 component of nuclear EMP is more closely proportional to the total energy
yield of the weapon.[34]

Weapon distance

A unique and important aspect of nuclear EMP is that all of the components of the electromagnetic
pulse are generated outside of the weapon. The important E1 component is generated by interaction
with the electrons in the upper atmosphere that are hit by gamma radiation from the weapon — and
the subsequent effects upon those electrons by the Earth's magnetic field.[30]

For high-altitude nuclear explosions, this means that much of the EMP is actually generated at a large
distance from the detonation (where the gamma radiation from the explosion hits the upper
atmosphere). This causes the electric field from the EMP to be remarkably uniform over the large
area affected.

According to the standard reference text on nuclear weapons effects published by the U.S.
Department of Defense, "The peak electric field (and its amplitude) at the Earth's surface from a high-
altitude burst will depend upon the explosion yield, the height of the burst, the location of the
observer, and the orientation with respect to the geomagnetic field.  As a general rule, however, the
field strength may be expected to be tens of kilovolts per meter over most of the area receiving the
EMP radiation."[35]

The same reference book also states that, "... over most of the area affected by the EMP the electric
field strength on the ground would exceed 0.5Emax.   For yields of less than a few hundred kilotons,
this would not necessarily be true because the field strength at the Earth's tangent could be
substantially less than 0.5Emax."[35]

(Emax refers to the maximum electric field strength in the affected area.)

In other words, the electric field strength in the entire area that is affected by the EMP will be fairly
uniform for weapons with a large gamma ray output; but for much smaller weapons, the electric field
may fall off at a comparatively faster rate at large distances from the detonation point.

It is the peak electric field of the EMP that determines the peak voltage induced in equipment and
other electrical conductors on the ground, and most of the damage is determined by induced
voltages.

For nuclear detonations within the atmosphere, the situation is more complex. Within the range of
gamma ray deposition, simple laws no longer hold as the air is ionised and there are other EMP
effects, such as a radial electric field due to the separation of Compton electrons from air molecules,
together with other complex phenomena. For a surface burst, absorption of gamma rays by air would
limit the range of gamma ray deposition to approximately 10 miles, while for a burst in the lower-
density air at high altitudes, the range of deposition would be far greater.


Non-nuclear electromagnetic pulse

Non-nuclear electromagnetic pulse (NNEMP) is an electromagnetic pulse generated without use of
nuclear weapons. There are a number of devices that can achieve this objective, ranging from a large
low-inductance capacitor bank discharged into a single-loop antenna or a microwave generator to an
explosively pumped flux compression generator. To achieve the frequency characteristics of the
pulse needed for optimal coupling into the target, wave-shaping circuits and/or microwave
generators are added between the pulse source and the antenna. A vacuum tube particularly suitable
for microwave conversion of high energy pulses is the vircator.[36]

NNEMP generators can be carried as a payload of bombs and cruise missiles, allowing construction of
electromagnetic bombs with diminished mechanical, thermal and ionizing radiation effects and
without the political consequences of deploying nuclear weapons.

The range of NNEMP weapons (non-nuclear electromagnetic bombs) is severely limited compared to
nuclear EMP. This is because nearly all NNEMP devices used as weapons require chemical
explosives as their initial energy source, but nuclear explosives have an energy yield on the order of
one million times that of chemical explosives of similar weight.[37]  In addition to the large difference
in the energy density of the initial energy source, the electromagnetic pulse from NNEMP weapons
must come from within the weapon itself, while nuclear weapons generate EMP as a secondary effect,
often at great distances from the detonation.[29]  These facts severely limit the range of NNEMP
weapons as compared to their nuclear counterparts, but allow for more surgical target discrimination.
The effect of small e-bombs has proven to be sufficient for certain terrorist or military operations.
Examples of such operations include the destruction of certain fragile electronic control systems of
the type critical to the operation of many ground vehicles and aircraft.[38]


Post–Cold War nuclear EMP attack scenarios

The United States military services have developed, and in some cases have published, a number of
hypothetical EMP attack scenarios.[44]

The United States EMP Commission was authorized by the United States Congress in Fiscal Year 2001,
and re-authorized in Fiscal Year 2006. The commission is formally known as the Commission to Assess
the Threat to the United States from Electromagnetic Pulse (EMP) Attack.[45]

The United States EMP Commission has brought together a group of notable scientists and
technologists to compile several reports. In 2008, the EMP Commission released the Critical National
Infrastructures Report.[34] This report describes, in as much detail as practical, the likely
consequences of a nuclear EMP on civilian infrastructures. Although this report was directed
specifically toward the United States, most of the information can obviously be generalized to the
civilian infrastructure of other industrialized countries.

The 2008 report was a followup to a more generalized report issued by the commission in 2004.[22][46]

In written testimony delivered to the United States Senate in 2005, an EMP Commission staff member
reported:
The EMP Commission sponsored a worldwide survey of foreign scientific and military literature to
evaluate the knowledge, and possibly the intentions, of foreign states with respect to
electromagnetic pulse (EMP) attack. The survey found that the physics of EMP phenomenon and the
military potential of EMP attack are widely understood in the international community, as reflected in
official and unofficial writings and statements. The survey of open sources over the past decade
finds that knowledge about EMP and EMP attack is evidenced in at least Britain, France, Germany,
Israel, Egypt, Taiwan, Sweden, Cuba, India, Pakistan, Iraq under Saddam Hussein, Iran, North Korea,
China and Russia. . . . Many foreign analysts–particularly in Iran, North Korea, China, and Russia–view
the United States as a potential aggressor that would be willing to use its entire panoply of weapons,
including nuclear weapons, in a first strike. They perceive the United States as having contingency
plans to make a nuclear EMP attack, and as being willing to execute those plans under a broad range
of circumstances. Russian and Chinese military scientists in open source writings describe the basic
principles of nuclear weapons designed specifically to generate an enhanced-EMP effect, that they
term "Super-EMP" weapons. "Super-EMP" weapons, according to these foreign open source writings,
can destroy even the best protected U.S. military and civilian electronic systems.[19]
This is the one I fear the most.....With so much of the country that is not prepared for this, and so
much of us are married to electronic equipment.....this will put us back in the stone age
See my personal
comments at the
very end!!
OK...BLA BLA BLA.....whats all this technical crap mean????
It means if a nuclear bomb, what many call a "DIRTY BOMB" gets exploded over this country,
depending how big it is and how far above the ground level it was exploded.......

EVERYTHING ELECTRIC, ELECTRONIC WILL BE
FRIED....  PERIOD.....NO MORE CIRCUITS...GONE
NO MORE CELL PHONES, COMPUTERS, MICROWAVE OVENS....
EVEN YOUR CAR WILL BE UNABLE TO BE USED EVER AGAIN!!!

YA GET ME CLEAR ENOUGH????? WE WILL BE THE FLINTSTONES!!!

WHAT CAN YOU DO???

1) Make a Faraday cage, and put one item of electronic necessity that you want, that you will be able
to power on your own, in the cage for safe guarding.
A) See Our page "
How to make a Faraday Cage" here!