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Saturday, February 17, 2007

"RH: Defending against manned/unmanned/stealth warplanes and Land attacks"

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From: Robert Ho (ho3@pacific.net.sg)
Subject: RH: How to defend against unmanned spy/warplanes
View: Complete Thread (17 articles)

Original Format

Newsgroups: soc.culture.singapore
Date: 2004-01-12 02:39:48 PST

RH: In my posting "RH: How to defend against enemy warplanes" [see
below], I proposed a possibly effective way to bring down enemy
warplanes by targetting the pilot instead of his plane. If my idea
works, the enemy will have to start developing remote-controlled
spy/warplanes, that is, without human pilots, since humans are the
weakest link in the entire warplane system.

Some of you thought that the obvious way around my idea is to control
the plane remotely from the ground. Well, I have an idea against that, too, that may possibly work.

For example, for a ground pilot to control the remote-controlled
spy/warplane, he must have a way of communicating with the plane. That is, through encoded transmissions to and from the plane.

These transmissions to the plane can be jammed. If the communications
to the plane are jammed, then the plane is out of control and will
eventually crash. However, preventing jamming of signals is pretty
well developed since it is quite obvious. So, relying on jamming alone will probably not work. [RH 1 Oct 2010 in bold]: However, most countries nowadays can make powerful multi-frequencies jammers that may work. Since the enemy warplanes have to be controlled from far away, outside the borders of the defending country, the defenders have the advantage of nearness to the remotely-controlled warplanes flying inside the defending country, plus the fact that their jammers, operated from the ground, can produce more powerful frequencies than those from enemy controllers who are operating either from naval ships, a big electronics plane or even from their own country through satellite retransmissions. So jamming may work. [RH 2 Oct 2010 in bold italics]: Not only should defending countries jammers produce all kinds of frequencies to confuse the enemy signals to its unmanned warplanes, the jammers should also produce anti sine waves in all frequencies to cancel out part of the enemy signals to its warplanes [using the principles of noise-cancelling discussed below]. Even if only a small part of the enemy signals are 'cancelled out', this will be enough to confuse the unmanned warplanes and thus disrupt their operations, maybe even crash the planes].


It does not matter if the signals are encoded to the highest
encryption. All we need to do is to capture any signals sent from the
enemy ground control to the plane, then cloning it exactly, then
sending this same cloned signal repeatedly to the plane. This will
eventually crash the plane.

It does not matter which signals are captured and cloned. Most
captured and cloned signals will work to crash the plane. For example, suppose the enemy ground control sends a signal to the plane to 'Turn left by 1 degree'. By capturing this signal, then cloning it and sending it repeatedly to the plane, the plane will keep turning left by 1 degree until it is flying around in circles, etc, until it
eventually crashes when the fuel runs out, etc.

We don't even have to decode the encrypted signal, which is very
difficult. Capturing and cloning the signal is much, much, easier. I
can think of no reason why this idea would not work. It is simple and
easy to capture the enemy's signals. Almost every country has the
means to do it. Even now, most countries are engaged in capturing
potential enemies' military communication signals [and trying to
decode them]. So, capturing and cloning the enemy's transmissions to
the remote-controlled planes is pretty easy.

Thus, almost any flight path change signals will work. Whether it is
to turn or to climb or to dive, etc. This idea, if it works, is pretty neat since it uses the enemy's own signals to defeat him. Again, the proximity advantage works. The enemy controllers will be well outside the defending country so their signals will travel longer and from further away than the defending country signals. Thus, the defending country should build a Great Wall of radio signals detectors and cloning facilities around its borders like a Great Wall. Better still if the defending country can build such radio frequencies detectors in forward bases outside its borders so as to capture the signals even earlier and sooner. If your spies and electronic monitoring can learn what frequencies and encryptions are being used, you will have a big advantage. [Defending countries should encourage enemy defectors and those with knowledge of the frequencies, encryptions and hardware to sell their knowledge for lots of money. This offer of lots of money should be an open and longstanding offer so potential enemy defectors can know in advance how much they can get for what kind of secrets. In addition to money, make the moral case that this selling of secrets will not hurt their country, only prevent it from attacking others, hence purely a defensive operation. If these defectors or your spies can get you these encryptions algorithms, you can seize control of the enemy warplanes, turn them back and even make them bomb or attack their own aircraft carriers, bases, etc]. Once the enemy controllers frequencies are captured, these frequencies can be cloned and sent repeatedly towards the enemy warplanes flying inside your defending country. Another method is to use the principles of the noise-cancelling headphones very common nowadays. These noise-cancelling headphones detect the frequencies of the unwanted and unpleasant noises, then create the exact opposite of these frequencies thereby 'cancelling' the noise so you hear nothing. These 'anti noise frequencies' are sometimes called 'white noise'. The frequencies of these cancelling or white noise is the exact opposite of the noise wave lengths, which are probably sine waves. However, sound waves are much slower than radio waves so the equipment to cancel the enemy controllers radio frequencies will have to capture and generate the anti signals much faster than for sound, but is not difficult. For best effect, the phases of the sine waves may have to be adjusted slightly forwards to perfectly cancel the enemy controllers signals.

Robert Ho
12 Jan 04
UK 1040 Singapore 1840


From: Robert Ho (ho3@pacific.net.sg)
Subject: RH: How to defend against enemy warplanes
View: Complete Thread (5 articles)
Original Format
Newsgroups: soc.culture.singapore
Date: 2003-12-25 20:08:32 PST


1. This is a purely defensive idea because it defends a country
against enemy warplanes; does not help it attack another.

2. That is, if enemy warplanes fly over your country/cities, it must
be because they are attacking you and you are defending against them.

3. The basic premise in this idea is that, when enemy warplanes fly
into your country, you should NOT try to destroy the planes
themselves, because that is more difficult; instead, you should try to destroy the pilots, because in the entire enemy warplane system of
pilot and plane, the weakest link is the human and not his machine.

4. Currently, air defence systems try to destroy the plane and not
the pilot. That has severe limitations.

5. For example, in order to destroy the plane, you have to use
relatively slow anti-aircraft missiles because only missiles can carry the explosive power up to the enemy aircraft to destroy it.

6. This missile can be thwarted because

a. it is relatively big and being metallic, can be detected by the
warplane's radar

b. it is relatively slow and can be tracked by the warplane thus
giving the pilot enough time to take counter and evasive measures

c. it uses a rocket engine which gives off a heat signature that can
also be tracked and countered or evaded

d. the missile has a limited range

7. If we were to target the pilot instead and not his plane, there
would be advantages overcoming the above limitations.

8. For example, instead of a missile, we could use lasers or some
other part of the electromagnetic spectrum that could cause instant
damage to human organs or tissues, etc. These electromagnetic waves
could include gamma rays or x-rays or parts of the more powerful and
harmful spectrum. They could include lasers.

9. Since such EM waves travel mostly at the speed of light, which is
186,000 miles per SECOND [300,000 km per SECOND], these EM waves are
so much faster than missiles, they practically shoot from the ground
defence unit or your flying defending planes to the enemy warplane in the sky almost instantly, giving no warning to the enemy pilot. Thus, you do not need superior warplanes or superior air to air missiles to stop an invading enemy warplane. Even if your defending planes are slow and inferior technology, as long as your defending planes can shoot lasers or powerful body-harming x-rays, gamma rays, etc, your planes can blind, injure or kill the enemy pilot, thus crashing his plane so stopping its mission. Ground-based laser or gamma rays shooters can be operated from almost anywhere, using electric power from the city's electricity grid or portable generators. [7 Oct 2010: When enemy pilots know they will most likely be blinded or suffer organ damage, they will refuse to attack a country that has EM weapons].

10. And because EM waves have practically no mass or weight, they
cannot be detected. They also do not give off a heat signature and so
cannot be detected.

11. EM waves have far longer range than missiles. EM waves like
lasers probably only gets slightly diffused by cloud and atmospheric
particles and some EM waves not at all.

12. In other words, EM waves have none of the limitations of the
above 6 a b c d.

13. Now, what could the EM waves do to human organs and tissues?

14. It would be enough to cause the pilot organ damage with resulting pain. This would be enough to defeat his mission and make him turn back. A pilot in pain cannot continue his mission. If his organ/s are destroyed or damaged, he may not even be able to turn back or land safely. So, we could be destroying his warplane as well.

15. Some EM waves penetrate even metal, like gamma and x-rays, for
example. So, the air defence ground unit shooting the lasers/EM waves
can simply aim at the plane and would hit the pilot within the plane. Planes cannot be thickly armoured because they cannot fly fast and well with thick armour. Warplanes have transparent plastic cockpit canopies which can be penetrated easily by lasers or gamma rays. It is easy to add a laser or gamma shooter to current anti-aircraft radar units. The anti-aircraft missiles may be removed or retained in the anti-aircraft unit but the laser or gamma shooter will be much, much faster and invisible to the enemy warplane's radar or other detectors. Laser and gamma shooters are thus easy to make and easy to fit into conventional anti-aircraft radar units. A few months ago, the US Navy and Raytheon Corp successfully test fired a laser to destroy 4 unmanned aircraft [ http://www.google.com.sg/search?hl=en&q=anti-aircraft+laser+shot+down+unmanned+drones&aq=f&aqi=&aql=&oq=&gs_rfai= ]. They simply bought 6 commercial or industrial lasers, combined them to make the laser weapon. Thus, this technology is easy for most countries to develop. Note that if you want to blind, injure or kill the pilot, not destroy his plane, the technology will be even easier to develop.

16. Some lasers can hit the eyeballs of the pilot and permanently
blind him, which will thwart his mission and also destroy his plane
because he cannot operate or land it after being blinded. Lasers are
now so common most homes have at least one or two, in the form of DVD
or CD players, etc. Practically every university Physics Lab have one. So, developing a laser to shoot pilots is not difficult. It is well within the technological capabilities of practically all countries. Developing other EM wave shooters is also not too difficult because technologies like x-rays are also well developed.

17. In short, shoot the pilot and not his warplane. He is the weakest link in the warplane systems. With him disabled, he cannot complete his mission or even land safely.

Robert Ho
26 Dec 03
UK 0408 Singapore 1208


[RH: 7 Oct 2010]:
i. The above ideas provide a good defence against manned or unmanned air attacks but the same EM weapon technology can work against an invading army on the ground, too. Because the EM anti-aircraft shooters can stop most attacking planes, the attackers will not be able to achieve air superiority, meaning that the defending country can deploy longstanding pre-prepared EM weapons without fear these will be destroyed by enemy planes [although accurate long-range missiles like cruise missiles will still destroy them, but even these may be shot down with EM shooters since EM waves travel at 186,000 miles a SECOND, far faster than missiles can travel].

ii. In land or ground invasions, the principal and most effective weapon is the battletank, then armoured personnel carriers [APCs], etc, and since, like warplanes, these are controlled by human beings, the same principle of "attack the man, not his machine" applies. EM shooters can blind, injure and kill the men controlling these tanks and apcs, so stopping the tanks and apcs. Even foot soldiers can be blinded by fast-moving laser shooters that rapidly sweep laser rays back and forth at the soldiers at eye-level, so a single fast-moving laser can blind many soldiers. Once a soldier is blinded, he instantly switches from being a war asset to a war liability because his fellow soldiers then have to look after a blind man, thus impeding their war missions and operations. Since being blinded is worse than being injured or killed, most soldiers will not even fight.

iii. Tanks and apcs are cramped inside so cannot carry spare or reserve tank commanders and spare tank drivers. Thus, EM or laser shooters ["blinders"] that can instantly blind the tank commander or the tank driver will effectively stop the tank, since there are no reserves or spares due to the cramped space inside tanks and apcs.

iv. Thus, my ideas of EM defensive warfare are cheap, so easy to develop they will be widely available and sold in a few years time, and will make air superiority almost impossible and even land invasions almost impossible. Thus, I have made invasions almost impossible. We should enter a new era of universal peace, with only small-scale skirmishes by small groups possible.

[22 Oct 2010: Defending against Stealth warplanes]:

1. I believe that stealth planes hide from ground radar by being coated with radar-absorbing coatings and also by their shapes, which reflect radar waves in directions other than back to the ground radar stations antenna dish, so thereby cannot be detected. Stealth planes may also project a stream of cool plasma to foil radar waves hitting the plane. As these technologies improve, the day may come when stealth planes become TOTALLY INVISIBLE, which they are only partially successful so far. What then for the defenders?

2. I will outline some general principles or theory of a possible way to detect stealth planes, that will work even if they become totally invisible to ground radar. However, these principles will take much research and work to realise but may be worth trying.

3. All planes, even stealth planes, push very hard through the air, which at higher and higher speeds, becomes more and more powerful in air resistance, meaning that the air is highly compressed in front of the plane, the higher the plane speed, the greater the compression. This compressed layer of air in front and over the plane, even extending behind it, changes in properties, some of which changes may be useful in detecting the plane. Sound waves? Probably not. Changes in refraction? Possible. But refraction of what kind of waves? Certainly not light waves because we know we can see through dense air same as thinner air. But we do know that some radar waves of certain wavelengths are certainly refracted by lighter or denser air. For example, radio waves used to transmit Korean singer RAIN's songs can bounce off certain layers of air. It is this bouncing or reflection that allows radio stations to reach much, much, further than they would otherwise if they had to rely on straight line of sight. Thus, different layers of air, even "thermal inversions", can create a Reflective Layer that reflects radio waves. Thus, we have a proof of principle.

4. So, suppose we spray radar or radio waves of the right frequencies at every centimetre of the sky we want to defend from stealth planes, then have enough radar or collecting dishes to collect the reflections, process these reflected signals data, eliminate the 'noise' or standard known false signals, what remains would be radar or radio signals that, on bouncing back from the ionosphere, gets distorted or refracted by the compressed air layers in front and surrounding the stealth plane. Voila, we have detected the invisible.

5. Easier written than done, of course, but a proven principle that will work. However, since the invisible plane will not bounce off any radar or radio waves, assuming it is perfectly stealth, what would bounce back from the sky? According to my this morning of research, one possibility is the ionosphere. It is long known that the ionosphere bounces back radio and even radar waves BUT WITH MANY COMPLICATIONS AND VARYING CONDITIONS. Even varying with the time of day. However, all these variations can be taken into account by a good algorithm [much, much, work] which will strip out the false signals leaving only the correct signal, meaning the signal from the refraction of compressed air around the stealth plane. The invisible becomes visible.

6. Much, much, work needs to be done to develop the algorithms so that all these variations of shifting layers of reflection can be taken in account and eliminated from the data leaving only the signal from the plane. These shifting layers and moving layers may even change from place to place over a large country, so the algorithms must also take into account the behaviours of the ionosphere over different parts of the country or different parts of the world, if you are selling these algorithms to different countries on the planet.

7. To defeat this idea, stealth planes may fly much slower or be made much smaller. Both will reduce their effectiveness as war machines. Simply by making our radio or radar collecting dishes more sensitive and developing better algorithms, we can still spot them. They can fly much, much, higher, in thinner and thinner air to reduce the compressed air signature of the plane but it will not work. Air too thin will not support jet engines. Too slow a speed will also not force enough air into the jet engines to produce thrust. There is also stall speed. Besides, US radar can currently track even a baseball in space, so most countries will be able to transmit radar or radio signals all the way to the various reflecting layers of the ionosphere.

8. My work is done. Yours begin. Good Luck!

9. However, given the numerous variables and complexities of bouncing radio or radar waves off the ionosphere, which continuously shifts and moves, as well as being affected by various phenomena including sunspots and solar flares, magnetic storms, etc, all this may make the idea very difficult to implement, so very costly and time consuming, requiring much work. To save all that, it may be easier to put some geostationary satellites into space stationed over your country. These satellites will produce the radio and radar waves and beam them towards the ground over your entire country, or better still, even spread further out if you have forward bases or friendly countries which let you operate receiving stations inside their borders.

10. Again, the principle is the same. You produce a steady stream of radio or radar waves directly from your satellites down to the ground over your entire country, or preferably, even spread further out, outside your borders. Thus, these continuous waves become kind of like the home or office security infra-red waves that trigger an alarm the moment a burglar breaks the beams of infra-red waves. In the same way, your satellites will continuously shoot waves down to your receiving stations on the ground and the moment a 'disturbance' in this transmission-receiving of waves is detected -- there you are, your stealth plane. [Planes create a huge air turbulence which is why along commercial air routes, planes are kept far apart, both from the plane in front as well as above and below, otherwise violent air turbulence accidents can happen, throwing the entire plane out of control]. I still do not know if radar and radio waves are the best ways to detect this air turbulence but you can explore all the possible ways to detect the air turbulence caused by jet planes flying fast. Even a stealth plane creates a huge 'wake' in the air, like water waves behind a fast and big boat.

11. Note that the ionosphere which bounces back some frequencies from the ground back to the ground, will also bounce some frequencies from the satellites back into space, instead of reaching the ground into your ground radar receivers. So you have to choose your frequencies carefully for maximum effect. This is not difficult.

12. Since each satellite will have to produce multiple frequencies of very strong signals, this will require power input of many hundreds of watts or even more, meaning that solar panels are probably not enough, so probably needs small nuclear power generators. Since there are no humans to be affected by the radioactive radiation, no thick shielding is needed, thus saving costly weight [to launch a kilogram into space costs at least half a million dollars for each kilo].

13. There is the slight danger that when such nuclear generators in the satellites fall to earth, they may become a radioactive hazard, so prepare to control the fall into a suitable ocean. Prepare also for the possibility that enemies may shoot down your satellites to land inside your country. All these are minor considerations compared with the important objective of detecting the air turbulence caused by stealth planes. You will probably have to shoot ahead of whatever turbulence you detect, depending on its speed, flight path, etc. If you use lasers/gamma shooters, etc, you should score a hit the millisecond you detect the plane, while high explosives missiles can damage a fairly big area of air so downing the plane even if detonated a distance away. You would probably spray the sky a fairly big area to ensure you hit the plane. This is not difficult. The difficult work is to detect and track the plane. Once you can do that, you are safe from attack. Good Luck.

[RH: 23 Oct 2010]:

14. I have googled and found that there have been several successful methods and equipment systems that can detect the air turbulence caused by jet planes, technically termed "wake vortices". Here are 3,050 results for [detecting wake vortex by spectral infrared radiometry]:


15. Here are 11,400 google search results for [LIDAR detection of wake vortices]:


16. Here are 6,650 results for [radar detection of wake vortices]:


17. Here are 143,000 results for [radar-acoustic detection of wake vortice]:


18. I finish with a general search term [equipment to detect wake vortices] for which there are 100,000 results. Clearly, when I began, I reasoned out general principles for detecting stealth warplanes and soon found that there already exists proven equipment and methodologies for detecting wake vortices, meaning that any defender can simply buy such existing equipment and couple these with conventional anti aircraft missiles or EM high power rays, etc. However, to defend a big country and not just a city or a military base, the equipment needs to be scaled much bigger to protect the entire country with reasonable success. This is not difficult because the basic research has been done and proven in principle and operations. Good Luck and Allahu Akbar!


Relevant readings:


E layer
The E layer is the middle layer, 90 km to 120 km above the surface of the Earth. Ionization is due to soft X-ray (1-10 nm) and far ultraviolet (UV) solar radiation ionization of molecular oxygen (O2). Normally, at oblique incidence, this layer can only reflect radio waves having frequencies lower than about 10 MHz and may contribute a bit to absorption on frequencies above. However during intense Sporadic E events the Es layer can reflect frequencies up to 50 MHz and higher.The vertical structure of the E layer is primarily determined by the competing effects of ionization and recombination. At night the E layer rapidly disappears because the primary source of ionization is no longer present. After sunset an increase in the height of the E layer maximum increases the range to which radio waves can travel by reflection from the layer.

The ionospheric layers

Ionospheric layers.
At night the F layer is the only layer of significant ionization present, while the ionization in the E and D layers is extremely low. During the day, the D and E layers become much more heavily ionized, as does the F layer, which develops an additional, weaker region of ionisation known as the F1 layer. The F2 layer persists by day and night and is the region mainly responsible for the refraction of radio waves.

The Es layer (sporadic E-layer) is characterized by small, thin clouds of intense ionization, which can support reflection of radio waves, rarely up to 225 MHz. Sporadic-E events may last for just a few minutes to several hours. Sporadic E propagation makes radio amateurs very excited, as propagation paths that are generally unreachable can open up. There are multiple causes of sporadic-E that are still being pursued by researchers. This propagation occurs most frequently during the summer months when high signal levels may be reached. The skip distances are generally around 1000 km (620 miles). VHF TV and FM broadcast DX'ers also get excited as their signals can be bounced back to Earth by Es. Distances for one hop propagation can be as close as 900 km [500 miles] or up to 2500 km (1,400 miles). Douple-hop reception over 3500 km (2,000 miles) is possible, too.
May be good...

F layer
The F layer or region, also known as the Appleton layer extends from about 200 km to more than 500 km above the surface of Earth. It is the densest point of the ionosphere, which implies signals penetrating this layer will escape into space. Beyond this layer is the topside ionosphere. Here extreme ultraviolet (UV, 10–100 nm) solar radiation ionizes atomic oxygen. The F layer consists of one layer at night, but during the day, a deformation often forms in the profile that is labeled F1. The F2 layer remains by day and night responsible for most skywave propagation of radio waves, facilitating high frequency (HF, or shortwave) radio communications over long distances.
From 1972 to 1975 NASA launched the AEROS and AEROS B satellites to study the F region.[2]

Complications, but some further principles:

Ionospheric model
An ionospheric model is a mathematical description of the ionosphere as a function of location, altitude, day of year, phase of the sun spot cycle and geomagnetic activity. Geophysically, the state of the ionospheric plasma may be described by four parameters: electron density, electron and ion temperatureand, since several species of ions are present, ionic composition. Radio propagation depends uniquely on electron density.
Models are usually expressed as computer programs. The model may be based on basic physics of the interactions of the ions and electrons with the neutral atmosphere and sun light, or it may be a statistical description based on a large number of observations or a combination of physics and observations. One of the most widely used models is the International Reference Ionosphere (IRI)[3](IRI 2007), which is based on data and specifies the four parameters just mentionned. The IRI is an international project sponsored by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI).[4] The major data sources are the worldwide network of ionosondes, the powerful incoherent scatter radars (Jicamarca, Arecibo, Millstone Hill, Malvern, St. Santin), the ISIS and Alouette topside sounders, and in situ instruments on several satellites and rockets. IRI is updated yearly. IRI will be established in 2009 by the International Organization for Standardization (ISO) as standard TS16457. IRI is accurate in describing the variation of the electron density from bottom of the ionosphere to the altitude of maximum density than in describing the total electron content (TEC).
[edit]Anomalies to the ideal model

Ionograms allow deducing not only the shape of the different layers but also the structure of theelectron/ion-plasma. Rough traces, indicating nonhomogeneity, are seen predominantly at night and at higher latitudes, and during disturbed conditions.
[edit]Winter anomaly
At mid-latitudes, the F2 layer daytime ion production is higher in the summer, as expected, since the sun shines more directly on the earth. However, there are seasonal changes in the molecular-to-atomic ratio of the neutral atmosphere that cause the summer ion loss rate to be even higher. The result is that the increase in the summertime loss overwhelms the increase in summertime production, and total F2ionization is actually lower in the local summer months. This effect is known as the winter anomaly. The anomaly is always present in the northern hemisphere, but is usually absent in the southern hemisphere during periods of low solar activity.
[edit]Equatorial anomaly

Electric currents created in sunward ionosphere.
Within approximately ± 20 degrees of the magnetic equator, is the equatorial anomaly. It is the occurrence of a trough of concentrated ionization in the F2 layer. The Earth's magnetic field lines are horizontal at the magnetic equator. Solar heating andtidal oscillations in the lower ionosphere move plasma up and across the magnetic field lines. This sets up a sheet of electric current in the E region which, with thehorizontal magnetic field, forces ionization up into the F layer, concentrating at ± 20 degrees from the magnetic equator. This phenomenon is known as theequatorial fountain.
[edit]Equatorial electrojet
The worldwide solar-driven wind results in the so-called Sq (solar quiet) current system in the E region of the Earth's ionosphere (100–130 km altitude). Resulting from this current is an electrostatic field directed E-W (dawn-dusk) in the equatorial day side of the ionosphere. At the magnetic dip equator, where the geomagnetic field is horizontal, this electric field results in an enhanced eastward current flow within ± 3 degrees of the magnetic equator, known as the equatorial electrojet.
[edit]Ionospheric perturbations

[edit]X-rays: sudden ionospheric disturbances (SID)
When the sun is active, strong solar flares can occur that will hit the Earth with hard X-rays on the sunlit side of the Earth. They will penetrate to the D-region, release electrons which will rapidly increase absorption causing a High Frequency (3-30 MHz) radio blackout. During this time Very Low Frequency (3 – 30 kHz) signals will become reflected by the D layer instead of the E layer, where the increased atmospheric density will usually increase the absorption of the wave, and thus dampen it. As soon as the X-rays end, the sudden ionospheric disturbance (SID) or radio black-out ends as the electrons in the D-region recombine rapidly and signal strengths return to normal.
[edit]Protons: polar cap absorption (PCA)
Associated with solar flares is a release of high-energy protons. These particles can hit the Earth within 15 minutes to 2 hours of the solar flare. The protons spiral around and down the magnetic field lines of the Earth and penetrate into the atmosphere near the magnetic poles increasing the ionization of the D and E layers. PCA's typically last anywhere from about an hour to several days, with an average of around 24 to 36 hours.
[edit]Geomagnetic storms
A geomagnetic storm is a temporary intense disturbance of the Earth's magnetosphere.
During a geomagnetic storm the F2 layer will become unstable, fragment, and may even disappear completely.
In the Northern and Southern pole regions of the Earth aurora will be observable in the sky.
Lightning can cause ionospheric perturbations in the D-region in one of two ways. The first is through VLF frequency radio waves launched into the magnetosphere. These so-called "whistler" mode waves can interact with radiation belt particles and cause them to precipitate onto the ionosphere, adding ionization to the D-region. These disturbances are called Lightning-induced Electron Precipitation (LEP) events.
Additional ionization can also occur from direct heating/ionization as a result of huge motions of charge in lightning strikes. These events are called Early/Fast.
In 1925, C. F. Wilson proposed a mechanism by which electrical discharge from lightning storms could propagate upwards from clouds to the ionosphere. Around the same time, Robert Watson-Watt, working at the Radio Research Station in Slough, UK, suggested that the ionospheric sporadic E layer (Es) appeared to be enhanced as a result of lightning but that more work was needed. In 2005, C. Davis and C. Johnson, working at the Rutherford Appleton Laboratory in Oxfordshire, UK, demonstrated that the Es layer was indeed enhanced as a result of lightning activity. Their subsequent research has focussed on the mechanism by which this process can occur.
[edit]Radio application

DX communication, popular among amateur radio enthusiasts, is a term given to communication over great distances. Thanks to the property of ionized atmospheric gases to refract high frequency (HF, orshortwave) radio waves, the ionosphere can be utilized to "bounce" a transmitted signal down to ground. Transcontinental HF-connections rely on up to 5 bounces, or hops. Such communications played an important role during World War II. Karl Rawer's most sophisticated prediction method[1] took account of several (zig-zag) paths, attenuation in the D-region and predicted the 11-years solar cycle by a method due to Wolfgang Gleißberg.
[edit]Mechanism of refraction
When a radio wave reaches the ionosphere, the electric field in the wave forces the electrons in the ionosphere into oscillation at the same frequency as the radio wave. Some of the radio-frequency energy is given up to this resonant oscillation. The oscillating electrons will then either be lost to recombination or will re-radiate the original wave energy. Total refraction can occur when the collision frequency of the ionosphere is less than the radio frequency, and if the electron density in the ionosphere is great enough.
The critical frequency is the limiting frequency at or below which a radio wave is reflected by an ionospheric layer at vertical incidence. If the transmitted frequency is higher than the plasma frequency of the ionosphere, then the electrons cannot respond fast enough, and they are not able to re-radiate the signal. It is calculated as shown below:

where N = electron density per cm3 and fcritical is in MHz.
The Maximum Usable Frequency (MUF) is defined as the upper frequency limit that can be used for transmission between two points at a specified time.

where α = angle of attack, the angle of the wave relative to the horizon, and sin is the sine function.
The cutoff frequency is the frequency below which a radio wave fails to penetrate a layer of the ionosphere at the incidence angle required for transmission between two specified points by refraction from the layer.
[edit]Other applications

The open system electrodynamic tether, which uses the ionosphere, is being researched. The space tetheruses plasma contactors and the ionosphere as parts of a circuit to extract energy from the Earth's magnetic field by electromagnetic induction.

Much of the work has been done already...
Ionograms show the virtual heights and critical frequencies of the ionospheric layers and which are measured by an ionosonde. An ionosonde sweeps a range of frequencies, usually from 0.1 to 30 MHz, transmitting at vertical incidence to the ionosphere. As the frequency increases, each wave is refracted less by the ionization in the layer, and so each penetrates further before it is reflected. Eventually, a frequency is reached that enables the wave to penetrate the layer without being reflected. For ordinary mode waves, this occurs when the transmitted frequency just exceeds the peak plasma, or critical, frequency of the layer. Tracings of the reflected high frequency radio pulses are known as ionograms. Reduction rules are given in:"URSI Handbook of Ionogram Interpretation and Reduction", edited byW.R.Piggott and Karl Rawer, Elsevier Amsterdam 1961. Translations in Chinese, French, Japanese, Russian were edited by national organisations.

Backscatter can work, too...

[edit]Incoherent scatter radars
Incoherent scatter radars operate above the critical frequencies. Therefore the technique allows to probe the ionosphere, unlike ionosondes, also above the electron density peaks. The thermal fluctuations of the electron density scattering the transmitted signals lack coherence, which gave the technique its name. Their power spectrum contains information not only on the density, but also on the ion and electron temperatures, ion masses and drift velocities.
[edit]Solar flux
Solar flux is a measurement of the intensity of solar radio emissions at a frequency of 2800 MHz made using a radio telescope located in Dominion Radio Astrophysical Observatory, Penticton, British Columbia, Canada[5]. Known also as the 10.7 cm flux (the wavelength of the radio signals at 2800 MHz), this solar radio emission has been shown to be proportional to sunspot activity. However, the level of the sun's ultraviolet and X-ray emissions is primarily responsible for causing ionization in the Earth's upper atmosphere. We now have data from the GOES spacecraft that measures the background X-ray flux from the sun, a parameter more closely related to the ionization levels in the ionosphere.
The A and K indices are a measurement of the behavior of the horizontal component of thegeomagnetic field. The K index uses a scale from 0 to 9 to measure the change in the horizontal component of the geomagnetic field. A new K index is determined at the Table Mountain Observatory, north of Boulder, Colorado.
The geomagnetic activity levels of the earth are measured by the fluctuation of the Earth's magnetic field in SI units called teslas (or in non-SI gauss, especially in older literature). The Earth's magnetic field is measured around the planet by many observatories. The data retrieved is processed and turned into measurement indices. Daily measurements for the entire planet are made available through an estimate of the ap index, called the planetary A-index (PAI).
[edit]Scientific research on ionospheric propagation
Scientists also are exploring the structure of the ionosphere by a wide variety of methods, including passive observations of optical and radio emissions generated in the ionosphere, bouncing radio waves of different frequencies from it, incoherent scatter radars such as the EISCAT, Sondre Stromfjord,Millstone Hill, Arecibo, and Jicamarca radars, coherent scatter radars such as the Super Dual Auroral Radar Network (SuperDARN) radars, and using special receivers to detect how the reflected waves have changed from the transmitted waves.
A variety of experiments, such as HAARP (High Frequency Active Auroral Research Program), involve high power radio transmitters to modify the properties of the ionosphere. These investigations focus on studying the properties and behavior of ionospheric plasma, with particular emphasis on being able to understand and use it to enhance communications and surveillance systems for both civilian and military purposes. HAARP was started in 1993 as a proposed twenty year experiment, and is currently active near Gakona, Alaska.
The SuperDARN radar project researches the high- and mid-latitudes using coherent backscatter of radio waves in the 8 to 20 MHz range. Coherent backscatter is similar to Bragg scattering in crystals and involves the constructive interference of scattering from ionospheric density irregularities. The project involves more than 11 different countries and multiple radars in both hemispheres.
Scientists are also examining the ionosphere by the changes to radio waves from satellites and stars passing through it. The Arecibo radio telescope located in Puerto Rico, was originally intended to study Earth's ionosphere.
[edit]Ionospheres on other planets and Titan

The atmosphere of Titan, the only moon known to have one, includes an ionosphere.[6] It ranges from about 1100 to 1300 km in altitude, and contains carbon compounds.
Planets with ionospheres (incomplete list):
Ionosphere of Venus Atmosphere of Venus#Upper atmosphere and ionosphere
Ionosphere of Uranus Atmosphere of Uranus#Ionosphere

In 1899, Nikola Tesla moved from New York to Colorado Springs, Colorado, where he would have room for his high-voltage, high-frequency experiments. Upon his arrival he told reporters that he was conducting wireless telegraphy experiments transmitting signals from Pikes Peak to Paris.[7] Tesla's diary contains explanations of his experiments concerning the ionosphere.[8]
Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) using a 152.4 m (500 ft) kite-supported antenna for reception. The transmitting station in Poldhu, Cornwall used a spark-gap transmitter to produce a signal with a frequency of approximately 500 kHz and a power of 100 times more than any radio signal previously produced. The message received was three dits, the Morse code for the letter S. To reach Newfoundland the signal would have to bounce off the ionosphere twice. Dr. Jack Belrose has recently contested this, however, based on theoretical and experimental work.[9] However, Marconi did achieve transatlantic wireless communications beyond a shadow of doubt in Glace Bay one year later.
In 1902, Oliver Heaviside proposed the existence of the Kennelly-Heaviside Layer of the ionosphere which bears his name. Heaviside's proposal included means by which radio signals are transmitted around the Earth's curvature. Heaviside's proposal, coupled with Planck's law of black body radiation, may have hampered the growth of radio astronomy for the detection of electromagnetic waves from celestial bodies until 1932 (and the development of high frequency radio transceivers). Also in 1902, Arthur Edwin Kennellydiscovered some of the ionosphere's radio-electrical properties.
In 1912, the U.S. Congress imposed the Radio Act of 1912 on amateur radio operators, limiting their operations to frequencies above 1.5 MHz (wavelength 200 meters or smaller). The government thought those frequencies were useless. This led to the discovery of HF radio propagation via the ionosphere in 1923.
In 1926, Scottish physicist Robert Watson-Watt introduced the term ionosphere in a letter published only in 1969 in Nature:
We have in quite recent years seen the universal adoption of the term ‘stratosphere’..and..the companion term ‘troposphere’... The term ‘ionosphere’, for the region in which the main characteristic is large scale ionisation with considerable mean free paths, appears appropriate as an addition to this series.
Edward V. Appleton was awarded a Nobel Prize in 1947 for his confirmation in 1927 of the existence of the ionosphere. Lloyd Berkner first measured the height and density of the ionosphere. This permitted the first complete theory of short wave radio propagation. Maurice V. Wilkes and J. A. Ratcliffe researched the topic of radio propagation of very long radio waves in the ionosphere. Vitaly Ginzburg has developed a theory of electromagnetic wave propagation in plasmas such as the ionosphere.
In 1962 the Canadian satellite Alouette 1 was launched to study the ionosphere. Following its success wereAlouette 2 in 1965 and the two ISIS satellites in 1969 and 1971, all for measuring the ionosphere.
[edit]See also

Van Allen radiation belt
Schumann resonances
International Reference Ionosphere
Earth-Ionosphere waveguide
Line-of-sight propagation
Ionospheric absorption
Tether propulsion
Canadian Geospace Monitoring
Pioneer Venus project
New Horizons
Soft gamma repeater
TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics)
International Geophysical Year
Upper Atmospheric Lightning
List of astronomical topics
List of electronics topics

^ a b K. Rawer. Wave Propagation in the Ionosphere. Kluwer Acad.Publ., Dordrecht 1993. ISBN 0-7923-0775-5
^ Yenne, Bill (1985). The Encyclopedia of US Spacecraft. Exeter Books (A Bison Book), New York. ISBN 0-671-07580-2.p.12 AEROS
^ D.Bilitza:International Reference Ionosphere 2000.Radio Sci.36,#2,261-275 2001
^ http://ccmc.gsfc.nasa.gov/modelweb/ionos/iri.html
^ http://www.swpc.noaa.gov/forecast_verification/F10.html
^ NASA/JPL: Titan's upper atmosphere Accessed 2010-08-25
^ Tesla biography at magnetricity.com
^ Tesla, Nikola, "The True Wireless". Electrical Experimenter, May 1919. (also at pbs.org)
^ John S. Belrose, "Fessenden and Marconi: Their Differing Technologies and Transatlantic Experiments During the First Decade of this Century". International Conference on 100 Years of Radio -- 5-7 September 1995.
Corum, J. F., and Corum, K. L., "A Physical Interpretation of the Colorado Springs Data". Proceedings of the Second International Tesla Symposium. Colorado Springs, Colorado, 1986.
Davies, K., 1990. Peter Peregrinus Ltd, London. ISBN 0-86341-186-X Ionospheric Radio.
Grotz, Toby, "The True Meaning of Wireless Transmission of power". Tesla : A Journal of Modern Science, 1997.
Hargreaves, J. K., "The Upper Atmosphere and Solar-Terrestrial Relations". Cambridge University Press, 1992,
Kelley, M. C, and Heelis, R. A., "The Earth's Ionosphere: Plasma Physics and Electrodynamics". Academic Press, 1989.
Leo F. McNamara. (1994) ISBN 0-89464-804-7 "Radio Amateurs Guide to the Ionosphere".
Rawer,K.:"Wave Propagation in the Ionosphere". Kluwer Academic Publ., Dordrecht 1993 ISBN 0-7923-0775-5.
D. Bilitza, "International Reference Ionosphere 2000,".Radio Science 36, #2, pp 261–275, 2001.
J. Lilensten et P.-L. Blelly: Du Soleil à la Terre, Aéronomie et météorologie de l'espace, Collection Grenoble Sciences, Université Joseph Fourier Grenoble I, 2000. ISBN 978-2-86883-467-6
P.-L. Blelly and D. Alcaydé, Ionosphere, in: Y. Kamide/A. Chian, Handbook of the Solar-Terrestrial Environment, Springer-Verlag Berlin Heidelberg, pp. 189-220, 2007. DOI: 10.1007/11367758_8
[edit]External links

Wikimedia Commons has media related to: Ionosphere
Look up ionosphere inWiktionary, the free dictionary.
Gehred, Paul, and Norm Cohen, SWPC's Radio User's Page.
Amsat-Italia project on Ionospheric propagation (ESA SWENET website)
was KN4LF NZ4O Solar Space Weather & Geomagnetic Data Archive
was KN4LF now NZ4O 160 Meter Radio Propagation Theory Notes Layman Level Explanations Of "Seemingly" Mysterious 160 Meter (MF/HF) Propagation Occurrences
USGS Geomagnetism Program
Encyclopaedia Britannica, Ionosphere and magnetosphere
Current Space Weather Conditions
Current Solar X-Ray Flux
Super Dual Auroral Radar Network
European Inchorent Scatter radar system
Millstone Hill incoherent scatter radar
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Troposphere • Stratosphere • Mesosphere • Thermosphere • Exosphere
Tropopause • Stratopause • Mesopause • Thermopause / Exobase
Ozone layer • Turbopause • Ionosphere
Categories: Radio frequency propagation | Atmosphere | Space plasmas | Plasma physics | Radio terminology

This Wikipedia page was last modified on 17 October 2010 at 15:14.


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