electromagnetic pulse (EMP) and Faraday cage
nuclear-generated EMP
A nuclear electromagnetic pulse (EMP) is a burst of "electromagnetic radiation" created by nuclear explosions. '
The resulting rapidly changing electric and magnetic fields may couple with electrical and electronic systems to produce "damaging current and voltage surges".
The pulse can easily span continent-sized areas, and this radiation can affect systems on land, sea, and air. ... 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.
Nuclear EMP is a complex multi-pulse, usually described in terms of three components, as defined by the International Electrotechnical Commission (IEC).
The three components of nuclear EMP, as defined by the IEC, are called "E1", "E2" and "E3".
The E1 pulse is the very fast component of nuclear EMP. E1 is a brief but intense electromagnetic field that induces high voltages in electrical conductors. E1 causes most of its damage by causing electrical breakdown voltages to be exceeded. E1 can destroy computers and communications equipment and it changes too quickly (nanoseconds) for ordinary surge protectors to provide effective protection from it. Fast-acting surge protectors (such as those using TVS diodes) will block the E1 pulse.
EMP events vary according to the altitude of the detonation.
The E2 component is generated by scattered gamma rays and inelastic gammas produced by neutrons. This E2 component is an "intermediate time" pulse that, by IEC definition, lasts from about 1 microsecond to 1 second after the explosion. E2 has many similarities to lightning,
The E3 component is different from E1 and E2. E3 is a much slower pulse, lasting tens to hundreds of seconds. It is caused by the nuclear detonation's temporary distortion of the Earth's magnetic field. The E3 component has similarities to a geomagnetic storm caused by a solar flare
The term "electromagnetic pulse" generally excludes
optical (infrared, visible, ultraviolet) and
ionizing (such as X-ray and gamma radiation) ranges.
In military terminology, a nuclear warhead detonated tens to hundreds of kilometers above the Earth's surface is known as a high-altitude electromagnetic pulse (HEMP) device.
nuclear weapon yields used during Cold War planning for EMP attacks were in the range of 1 to 10 megatons This is roughly 50 to 500 times the size of the Hiroshima and Nagasaki bombs. '
Physicists have testified at Congressional hearings that weapons with yields of 10 kilotons or less can produce a large EMP
The EMP at a fixed distance from an explosion increases at most as the square root of the yield. This means that although a 10 kiloton weapon has only 0.7% of the 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 low yield pure nuclear fission weapons, a 10 kiloton bomb can easily be 5 x 8% = 40% as powerful as the 1.44 megaton Starfish Prime at producing EMP.
The total prompt gamma ray energy in a fission explosion is 3.5% of the yield, but in a 10 kiloton detonation the triggering explosive around the bomb core absorbs about 85% of the prompt gamma rays, so the output is only about 0.5% of the yield.
Thermonuclear weapons are also less efficient at producing EMP because the first stage can pre-ionize the air
which becomes conductive and hence rapidly shorts out the Compton currents generated by the fusion 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.
Effects of a HEMP device depend on
the altitude of the detonation,
energy yield,
gamma ray output,
interactions with the Earth's magnetic field and
electromagnetic shielding of targets.
Effects
Older, vacuum tube (valve) based equipment is generally much less vulnerable to nuclear EMP than solid state equipment
Equipment that is running at the time of an EMP is more vulnerable
An EMP would probably not affect most cars
small electronic devices, such as wristwatches and cell phones, would most likely withstand an EMP
EMP, it will generally not flow out into human or animal bodies, and thus contact is safe.
low-altitude bursts were negative pulses
The high-altitude nuclear tests increased the awareness of high-altitude nuclear EMP beyond the original group of defense scientists.
The larger scientific community became aware of the significance of the EMP.
Starfish Prime
was a high-altitude nuclear test. It was launched from Johnston Island, and was the largest nuclear test conducted in outer space.
The 1.45 megaton explosion took place at an altitude of 250 miles.
Starfish Prime caused an EMP, which was far larger than expected, so much larger that it drove much of the instrumentation off scale, causing great difficulty in getting accurate measurements.
It caused electrical damage in Hawaii, about 898 miles away from the detonation point,
knocking out streetlights
setting off numerous burglar alarms and
damaging a telephone company microwave link that shut down telephone communication from Kauai to the other Hawaiian islands.
high-energy electrons became trapped and formed radiation belts around the Earth.
three satellites in low Earth orbit were disabled.
man-made radiation belts eventually caused six or more satellites to fail[
some Starfish electrons had remained for 5 years.[19]
Operation Fishbowl was a series of high-altitude nuclear tests
The EMP generated by a high-altitude explosion had very significant differences from the EMP generated by nuclear explosions closer to the surface.
high-altitude nuclear tests produce a number of unique geophysical phenomena at the opposite end of the magnetic field line of the Earth's magnetic field
new theory about the generation of nuclear EMP was developed by Los Alamos physicist Conrad Longmire in 1963, and it is the high-altitude nuclear EMP theory that is still used today
Fishbowl; high altitude effects test, W-49 warhead/Mk-4 RV on Thor missile. Burst seen in Hawaii, Kwajelein (1,600 mi (2,600 km) away), EMP effects in Oahu. Destroyed several satellites, including Telstar I, with radiation belt.
Faraday cage
an enclosure used to block electromagnetic fields. \\
A Faraday shield may be formed by a continuous covering of conductive material
a Faraday cage, by a mesh of such materials.
A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior.
This phenomenon is used to protect sensitive electronic equipment from external radio frequency interference (RFI).
Faraday cages are also used to enclose devices that produce RFI, such as radio transmitters, to prevent their radio waves from interfering with other nearby equipment.
They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior.
they shield the interior from external electromagnetic radiation if the conductor is thick enough and any holes are significantly smaller than the wavelength of the radiation.
For example, certain computer forensic test procedures can be carried out within a screened room. These rooms are spaces that are completely enclosed by one or more layers of
a fine metal mesh or
perforated sheet metal.
The metal layers are grounded , and thus they block a large amount of the electromagnetic interference.
They provide less attenuation from outgoing transmissions versus incoming:
they can shield EMP waves from natural phenomena very effectively,
but a tracking device, especially in upper frequencies, may be able to penetrate from within the cage (e.g., some cell phones operate at various radio frequencies so while one cell phone may not work, another one will).
A common misconception is that a Faraday cage provides full blockage or attenuation;
this is not true.
The reception or transmission of radio waves, to or from an antenna within a Faraday cage is heavily attenuated or blocked by the cage;
however, a Faraday cage has varied attenuation depending on
wave form,
frequency or
distance from receiver/transmitter, and
receiver/transmitter power.
Near-field high-powered frequency transmissions like HF RFID are more likely to penetrate.
Solid cages generally attenuate fields over a broader range of frequencies than mesh cages.
A nuclear electromagnetic pulse (EMP) is a burst of "electromagnetic radiation" created by nuclear explosions. '
The resulting rapidly changing electric and magnetic fields may couple with electrical and electronic systems to produce "damaging current and voltage surges".
The pulse can easily span continent-sized areas, and this radiation can affect systems on land, sea, and air. ... 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.
Nuclear EMP is a complex multi-pulse, usually described in terms of three components, as defined by the International Electrotechnical Commission (IEC).
The three components of nuclear EMP, as defined by the IEC, are called "E1", "E2" and "E3".
The E1 pulse is the very fast component of nuclear EMP. E1 is a brief but intense electromagnetic field that induces high voltages in electrical conductors. E1 causes most of its damage by causing electrical breakdown voltages to be exceeded. E1 can destroy computers and communications equipment and it changes too quickly (nanoseconds) for ordinary surge protectors to provide effective protection from it. Fast-acting surge protectors (such as those using TVS diodes) will block the E1 pulse.
EMP events vary according to the altitude of the detonation.
The E2 component is generated by scattered gamma rays and inelastic gammas produced by neutrons. This E2 component is an "intermediate time" pulse that, by IEC definition, lasts from about 1 microsecond to 1 second after the explosion. E2 has many similarities to lightning,
The E3 component is different from E1 and E2. E3 is a much slower pulse, lasting tens to hundreds of seconds. It is caused by the nuclear detonation's temporary distortion of the Earth's magnetic field. The E3 component has similarities to a geomagnetic storm caused by a solar flare
The term "electromagnetic pulse" generally excludes
optical (infrared, visible, ultraviolet) and
ionizing (such as X-ray and gamma radiation) ranges.
In military terminology, a nuclear warhead detonated tens to hundreds of kilometers above the Earth's surface is known as a high-altitude electromagnetic pulse (HEMP) device.
nuclear weapon yields used during Cold War planning for EMP attacks were in the range of 1 to 10 megatons This is roughly 50 to 500 times the size of the Hiroshima and Nagasaki bombs. '
Physicists have testified at Congressional hearings that weapons with yields of 10 kilotons or less can produce a large EMP
The EMP at a fixed distance from an explosion increases at most as the square root of the yield. This means that although a 10 kiloton weapon has only 0.7% of the 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 low yield pure nuclear fission weapons, a 10 kiloton bomb can easily be 5 x 8% = 40% as powerful as the 1.44 megaton Starfish Prime at producing EMP.
The total prompt gamma ray energy in a fission explosion is 3.5% of the yield, but in a 10 kiloton detonation the triggering explosive around the bomb core absorbs about 85% of the prompt gamma rays, so the output is only about 0.5% of the yield.
Thermonuclear weapons are also less efficient at producing EMP because the first stage can pre-ionize the air
which becomes conductive and hence rapidly shorts out the Compton currents generated by the fusion 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.
Effects of a HEMP device depend on
the altitude of the detonation,
energy yield,
gamma ray output,
interactions with the Earth's magnetic field and
electromagnetic shielding of targets.
Effects
Older, vacuum tube (valve) based equipment is generally much less vulnerable to nuclear EMP than solid state equipment
Equipment that is running at the time of an EMP is more vulnerable
An EMP would probably not affect most cars
small electronic devices, such as wristwatches and cell phones, would most likely withstand an EMP
EMP, it will generally not flow out into human or animal bodies, and thus contact is safe.
low-altitude bursts were negative pulses
The high-altitude nuclear tests increased the awareness of high-altitude nuclear EMP beyond the original group of defense scientists.
The larger scientific community became aware of the significance of the EMP.
Starfish Prime
was a high-altitude nuclear test. It was launched from Johnston Island, and was the largest nuclear test conducted in outer space.
The 1.45 megaton explosion took place at an altitude of 250 miles.
Starfish Prime caused an EMP, which was far larger than expected, so much larger that it drove much of the instrumentation off scale, causing great difficulty in getting accurate measurements.
It caused electrical damage in Hawaii, about 898 miles away from the detonation point,
knocking out streetlights
setting off numerous burglar alarms and
damaging a telephone company microwave link that shut down telephone communication from Kauai to the other Hawaiian islands.
high-energy electrons became trapped and formed radiation belts around the Earth.
three satellites in low Earth orbit were disabled.
man-made radiation belts eventually caused six or more satellites to fail[
some Starfish electrons had remained for 5 years.[19]
Operation Fishbowl was a series of high-altitude nuclear tests
The EMP generated by a high-altitude explosion had very significant differences from the EMP generated by nuclear explosions closer to the surface.
high-altitude nuclear tests produce a number of unique geophysical phenomena at the opposite end of the magnetic field line of the Earth's magnetic field
new theory about the generation of nuclear EMP was developed by Los Alamos physicist Conrad Longmire in 1963, and it is the high-altitude nuclear EMP theory that is still used today
Fishbowl; high altitude effects test, W-49 warhead/Mk-4 RV on Thor missile. Burst seen in Hawaii, Kwajelein (1,600 mi (2,600 km) away), EMP effects in Oahu. Destroyed several satellites, including Telstar I, with radiation belt.
Faraday cage
an enclosure used to block electromagnetic fields. \\
A Faraday shield may be formed by a continuous covering of conductive material
a Faraday cage, by a mesh of such materials.
A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior.
This phenomenon is used to protect sensitive electronic equipment from external radio frequency interference (RFI).
Faraday cages are also used to enclose devices that produce RFI, such as radio transmitters, to prevent their radio waves from interfering with other nearby equipment.
They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior.
they shield the interior from external electromagnetic radiation if the conductor is thick enough and any holes are significantly smaller than the wavelength of the radiation.
For example, certain computer forensic test procedures can be carried out within a screened room. These rooms are spaces that are completely enclosed by one or more layers of
a fine metal mesh or
perforated sheet metal.
The metal layers are grounded , and thus they block a large amount of the electromagnetic interference.
They provide less attenuation from outgoing transmissions versus incoming:
they can shield EMP waves from natural phenomena very effectively,
but a tracking device, especially in upper frequencies, may be able to penetrate from within the cage (e.g., some cell phones operate at various radio frequencies so while one cell phone may not work, another one will).
A common misconception is that a Faraday cage provides full blockage or attenuation;
this is not true.
The reception or transmission of radio waves, to or from an antenna within a Faraday cage is heavily attenuated or blocked by the cage;
however, a Faraday cage has varied attenuation depending on
wave form,
frequency or
distance from receiver/transmitter, and
receiver/transmitter power.
Near-field high-powered frequency transmissions like HF RFID are more likely to penetrate.
Solid cages generally attenuate fields over a broader range of frequencies than mesh cages.
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