The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere. Atmospheric electricity is the regular diurnal variations of the Earth 's atmospheric electromagnetic network (or more broadly any A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. Radio propagation is a term used to explain how Radio waves behave when they are Transmitted, or are propagated from one point on the Earth It is located in the Thermosphere. The thermosphere is the layer of the Earth's atmosphere directly above the Mesosphere and directly below the Exosphere.

Contents 1 Geophysics 2 The ionospheric layers 2.1 D layer 2.2 E layer 2.3 ES 2.4 F layer 2.5 Ionospheric model 3 Anomalies to the ideal model 3.1 Winter anomaly 3.2 Equatorial anomaly 3.3 Equatorial electrojet 4 Ionospheric perturbations 4.1 X-rays: sudden ionospheric disturbances (SID) 4.2 Protons: polar cap absorption (PCA) 4.3 Geomagnetic storms 4.4 Lightning 5 Radio application 6 Other applications 7 Measurements 7.1 Ionograms 7.2 Incoherent scatter radars 7.3 Solar flux 7.4 Scientific research on ionospheric propagation 8 History 9 References 10 See also 11 External links

Geophysics

The lowest part of the Earth's atmosphere is called the troposphere and it extends from the surface up to about 10 km (6 miles). Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand The atmosphere above 10 km is called the stratosphere, followed by the mesosphere. The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. This article is about the atmospheric mesosphere for the Earth's mantle see Mesosphere (mantle. It is in the stratosphere that incoming solar radiation creates the ozone layer. The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 At heights of above 80 km (50 miles), in the thermosphere, the atmosphere is so thin that free electrons can exist for short periods of time before they are captured by a nearby positive ion. The thermosphere is the layer of the Earth's atmosphere directly above the Mesosphere and directly below the Exosphere. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge The number of these free electrons is sufficient to affect radio propagation. Radio propagation is a term used to explain how Radio waves behave when they are Transmitted, or are propagated from one point on the Earth This portion of the atmosphere is ionized and contains a plasma which is referred to as the ionosphere. In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound In a plasma, the negative free electrons and the positive ions are attracted to each other by the electromagnetic force, but they are too energetic to stay fixed together in an electrically neutral molecule.

Solar radiation at ultraviolet (UV) and shorter X-Ray wavelengths is considered to be ionizing since photons at these frequencies are capable of dislodging an electron from a neutral gas atom or molecule during a collision. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays X-radiation (composed of X-rays) is a form of Electromagnetic radiation. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by At the same time, however, an opposing process called recombination begins to take place in which a free electron is "captured" by a positive ion if it moves close enough to it. As the gas density increases at lower altitudes, the recombination process accelerates since the gas molecules and ions are closer together. The point of balance between these two processes determines the degree of ionization present at any given time.

The ionization depends primarily on the Sun and its activity. The Sun (Sol is the Star at the center of the Solar System. Solar variations are changes in the amount of Solar radiation emitted by the Sun. The amount of ionization in the ionosphere varies greatly with the amount of radiation received from the sun. Thus there is a diurnal (time of day) effect and a seasonal effect. The local winter hemisphere is tipped away from the Sun, thus there is less received solar radiation. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The activity of the sun is associated with the sunspot cycle, with more radiation occurring with more sunspots. Radiation received also varies with geographical location (polar, auroral zones, mid-latitudes, and equatorial regions). There are also mechanisms that disturb the ionosphere and decrease the ionization. There are disturbances such as solar flares and the associated release of charged particles into the solar wind which reaches the Earth and interacts with its geomagnetic field. A solar flare is a violent explosion in a star's (like the Sun 's atmosphere releasing as much Energy as 6 × 1025 Joules Solar flares The solar wind is a Stream of charged particles&mdasha plasma &mdashthat are ejected from the upper atmosphere of the Sun. Earth 's magnetic field (and the surface magnetic field) is approximately a Magnetic dipole, with one pole near the North pole (see

The ionospheric layers

Solar radiation, acting on the different compositions of the atmosphere with height, generates layers of ionization:

D layer

The D layer is the innermost layer, 50 km to 90 km above the surface of the Earth. The D region is the portion of the Ionosphere that exists approximately 50 to 95 km above the surface of the Earth Ionization here is due to Lyman series-alpha hydrogen radiation at a wavelength of 121. In Physics, the Lyman series is the series of transitions and resulting Emission lines of the Hydrogen Atom as an Electron goes from In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. 5 nanometre (nm) ionizing nitric oxide (NO). A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a Nitric oxide or nitrogen monoxide is a Chemical compound with Chemical formula N[[Oxygen O]] In addition, when the sun is active with 50 or more sunspots, hard X-rays (wavelength < 1 nm) ionize the air (N₂, O₂). X-radiation (composed of X-rays) is a form of Electromagnetic radiation. During the night cosmic rays produce a residual amount of ionization. For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on Recombination is high in the D layer, thus the net ionization effect is very low and as a result high-frequency (HF) radio waves aren't reflected by the D layer. Radio waves are electromagnetic waves occurring on the Radio frequency portion of the Electromagnetic spectrum. The frequency of collision between electrons and other particles in this region during the day is about 10 million collisions per second. The D layer is mainly responsible for absorption of HF radio waves, particularly at 10 MHz and below, with progressively smaller absorption as the frequency gets higher. Ionospheric absorption (or ISAB is the scientific name for absorption occurring as a result of the interaction between various types of electromagnetic waves and The absorption is small at night and greatest about midday. The layer reduces greatly after sunset, but remains due to galactic cosmic rays. Galactic cosmic rays ( GCRs) consist of those Cosmic rays that enter the solar system from the outside A common example of the D layer in action is the disappearance of distant AM broadcast band stations in the daytime. Broadcast band commonly refers to several segments of the Radio spectrum.

During solar proton events, ionization can reach unusually high levels in the D-region over the high and polar latitudes. A Solar proton event occurs when Protons emitted by the Sun become accelerated to very high energies either close to the Sun during a Solar flare or in interplanetary Such events are known as Polar Cap Absorption (or PCA) events, because the increased ionization significantly enhances the absorption of radio signals passing through the region. In fact, absorption levels can increase by many tens of dB during intense events, which is enough to absorb most (if not all) transpolar HF radio signal transmissions. Such events typically last less than 24 to 48 hours.

E layer

The E layer is the middle layer, 90 km to 120 km above the surface of the Earth. The Kennelly-Heaviside layer, also known as the E region or simply the Heaviside layer, is a layer of ionised Gas occurring at 90&ndash150 km Ionization is due to soft X-ray (1-10 nm) and far ultraviolet (UV) solar radiation ionization of molecular oxygen (O₂). Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the This layer can only reflect radio waves having frequencies less than about 10 MHz. It has a negative effect on frequencies above 10 MHz due to its partial absorption of these waves. The vertical structure of the E layer is primarily determined by the competing effects of ionization and recombination. At night the E layer begins to disappear because the primary source of ionization is no longer present. This results in an increase in the height where the layer maximizes because recombination is faster in the lower layers. Diurnal changes in the high altitude neutral winds also plays a role. The increase in the height of the E layer maximum increases the range to which radio waves can travel by reflection from the layer.

This region is also known as the Kennelly-Heaviside Layer layer or simply the Heaviside layer. The Kennelly-Heaviside layer, also known as the E region or simply the Heaviside layer, is a layer of ionised Gas occurring at 90&ndash150 km Its existence was predicted in 1902 independently and almost simultaneously by the American electrical engineer Arthur Edwin Kennelly (1861-1939) and the British physicist Oliver Heaviside (1850-1925). Arthur Edwin Kennelly ( December 17, 1861 - June 18, 1939) was an Indian American Electrical engineer. However, it was not until 1924 that its existence was detected by Edward V. Appleton. Sir Edward Victor Appleton, GBE ( September 6, 1892 – April 21, 1965) was an English Physicist.

E_S

The E_s layer or sporadic E-layer. Sporadic E propagation is characterized by small clouds of intense ionization, which can support radio wave reflections from 25 – 225 MHz. Sporadic E or Es is an unusual form of Radio propagation utilizing characteristics of the earth's Ionosphere. Sporadic-E events may last for just a few minutes to several hours and make radio amateurs very excited, as propagation paths which 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 with major occurrences during the summer, and minor occurrences during the winter. During the summer, this mode is popular due to its high signal levels. The skip distances are generally around 1000km (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 short hop events can be as close as 500 miles or up to 1,400 (or more) for a long, single hop. Douple-hop reception over 2,000 miles is possible, too.

F layer

The F layer or region, also known as the Appleton layer, is 120 km to 400 km above the surface of the Earth. The F region of the Ionosphere is home to the F Layer of ionization also called the Appleton layer, after the English physicist Edward Appleton It is the top most layer of the ionosphere. Here extreme ultraviolet (UV) (10-100 nm) solar radiation ionizes atomic oxygen (O). Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the The F region is the most important part of the ionosphere in terms of HF communications. The F layer combines into one layer at night, and in the presence of sunlight (during daytime), it divides into two layers, the F₁ and F₂. The F layers are responsible for most skywave propagation of radio waves, and are thickest and most reflective of radio on the side of the Earth facing the sun. Skywave is the propagation of electromagnetic waves bent (refracted back to the Earth's surface by the Ionosphere. Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light.

From 1972-1975 NASA launched AEROS and AEROS B satellites to study the F-region. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program AEROS Satellite was to study the Science of the upper Atmosphere and Ionospheric F region 's Solar Ultraviolet ^[1]

Ionospheric model

The atmospheric physics community contributes to the definition and maintenance of an ionospheric model: the International Reference Ionosphere, through a series of academic committees and conferences. As discoveries are made and generally accepted, the model is improved. (IRI85-6)

Anomalies to the ideal model

The statements above assumed that each layer was smooth and uniform. In reality the ionosphere is a lumpy, cloudy layer with irregular patches of ionization.

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 F₂ ionization is actually lower, not higher, 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.

Equatorial anomaly

Within approximately ± 20 degrees of the magnetic equator, is the equatorial anomaly. The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the 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. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges Solar heating and tidal oscillations in the lower ionosphere move plasma up and across the magnetic field lines. Characteristics A tide is a repeated cycle of sea level changes in the following stages Over several hours the water rises or advances up a beach in the flood This sets up a sheet of electric current in the E region which, with the horizontal magnetic field, forces ionization up into the F layer, concentrating at ± 20 degrees from the magnetic equator. In Astronomy, Geography, Geometry and related sciences and contexts a plane is said to be horizontal at a given point if it is locally This phenomenon is known as the equatorial fountain.

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. The equatorial electrojet ( EEJ) is a narrow ribbon of current flowing eastward in the day time equatorial region of the Ionosphere.

Ionospheric perturbations

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. A solar flare is a violent explosion in a star's (like the Sun 's atmosphere releasing as much Energy as 6 × 1025 Joules Solar flares 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. A sudden ionospheric disturbance (SID is an abnormally high ionization/ plasma density in the D region of the Ionosphere caused by a Solar

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.

Geomagnetic storms

A geomagnetic storm is a temporary intense disturbance of the Earth's magnetosphere. A geomagnetic storm or solar storm is a temporary disturbance of the Earth 's Magnetosphere caused by a disturbance in Space weather. A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object.

• 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

Lightning can cause ionospheric perturbations in the D-region one of two ways. Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or The first is through VLF frequency radio waves launched into the magnetosphere. A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. 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.

Radio application

DX communication, popular among amateur radio enthusiasts, is a term given to communication over great distances. DXing is the hobby of tuning in and identifying distant Radio or Television signals or making two way radio contact with distant stations in Amateur radio Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications When using High-Frequency bands, the ionosphere is utilized to refract the transmitted radio beam. Refraction is the change in direction of a Wave due to a change in its Speed. The beam returns to the Earth's surface, and may then be reflected back into the ionosphere for a second bounce.

Radio waves "hop" from the Earth to the ionosphere and back to the Earth. Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. In Telecommunication, the term hop has the following meanings The excursion of a Radio wave from the Earth to the Ionosphere 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. In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can Oscillation is the repetitive variation typically in Time, of some measure about a central value (often a point of Equilibrium) or between two or more different states Some of the radio wave energy is given up to this mechanical oscillation. The oscillating electron 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 refracted by an ionospheric layer at vertical incidence. Angle of incidence is a measure of deviation of something from "straight on" for example in the approach of a ray to a surface or the angle 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. Plasma oscillations, also known as " Langmuir waves " (after Irving Langmuir) are rapid oscillations of the electron density in conducting media such as It is calculated as shown below:

where N = electron density per cm³ and f_critical 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. Angle of attack ( AOA, \alpha Greek letter alpha) is a term used in Aerodynamics to describe the Angle between the The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates

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. In Physics and Electrical engineering, a cutoff frequency, corner frequency, or break frequency is a boundary in a system's Frequency

Other applications

The open system space tether, which uses the ionosphere, is being researched. Tether propulsion systems are proposals to use long very strong cables (known as Tethers to change the velocity of Spacecraft. The space tether uses plasma contactors and the ionosphere as parts of a circuit to extract energy from the Earth's magnetic field by electromagnetic induction. Faraday's law of induction describes an important basic law of electromagnetism which is involved in the working of Transformers Inductors and many forms of

Measurements

Ionograms

Ionograms show the virtual heights and critical frequencies of the ionospheric layers and which are measured by an ionosonde. A ionosonde, or chirpsounder, is a special Radar for the examinatation of the Ionosphere. 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.

Incoherent scatter radars

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 Ottawa, Canada. A radio telescope is a form of directional Radio antenna used in Radio astronomy and in tracking and collecting data from Satellites Ottawa (ˈɒtəwə or sometimes /ˈɒtəwɑː/ is the Capital of Canada and the country's fourth largest municipality. 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 Geostationary Operational Environmental Satellite (or GOES) program is a key element in United States' National Weather Service (NWS operations

• The A and K indices are a measurement of the behavior of the horizontal component of the geomagnetic field. The A-index provides a daily average level for geomagnetic activity based on the K-index. The relationship between K Kp and estimated Kp The official planetary Kp index is derived by calculating a weighted average of K-indices from a network of geomagnetic 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. Table Mountain is a flat-topped Mountain forming a prominent landmark overlooking the city of Cape Town in South Africa, and is featured in the Boulder is a Home Rule Municipality that is the County seat and most populous city of Boulder County, Colorado, in the United States The State of Colorado ( or chiefly by nonresidents) is a state located in the Rocky Mountain region of the United States of America.
• The geomagnetic activity levels of the earth are measured by the fluctuation of the Earth's magnetic field in SI units called tesla (unit)s (or in non-SI gauss, especially in older literature). The tesla (symbol T) is the SI derived unit of Magnetic field B (which is also known as "magnetic flux density" and "magnetic The gauss, abbreviated as G is the Cgs unit of Magnetic field B (which is also known as "magnetic flux density" and "magnetic 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).

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. The Super Dual Auroral Radar Network (SuperDARN is an international Radar network for studying the upper Atmosphere and Ionosphere, comprised of eleven

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. HAARP is often confused with Project HARP, the High Altitude Research Project (a joint project of The Pentagon and the Canadian Department of National Defence 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. There is concern among many members of the scientific community regarding the dangers involved in disturbing the ionosphere.

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. The Arecibo Observatory is a very sensitive Radio telescope located approximately south-southwest from the town of Arecibo in Puerto Rico. Puerto Rico (ˌpwertoˈriko officially the Commonwealth of Puerto Rico ("Estado Libre Asociado de Puerto Rico" {{lang-en|"Associated Free State of Puerto Rico"}}

History

Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) using a 152. Marchese Guglielmo Marconi mar'koni (25 April 1874 – 20 July 1937 was an Italian inventor best known for his development of a Radiotelegraph system Events 627 - Battle of Nineveh: A Byzantine army under Emperor Heraclius defeats Emperor Khosrau II 's Persian Year 1901 ( MCMI) was a Common year starting on Tuesday (link will display calendar of the Gregorian calendar (or a Common year starting St John's (ˌseɪntˈdʒanz French Saint-Jean) is the provincial capital of Newfoundland and Labrador, Canada and located on the eastern tip Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page 4 m (500 foot) 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. Poldhu is a small area in south Cornwall, England, UK, situated on the Lizard Peninsula it comprises Poldhu Point and Poldhu Cove The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. The message received was three dots, the Morse code for the letter S. Morse code is a Character encoding for transmitting telegraphic information using standardized sequences of short and long elements to represent the letters numerals 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. ^[2] 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 Kennelly discovered some of the ionosphere's radio-electrical properties. Year 1902 ( MCMII) was a Common year starting on Wednesday (link will display calendar of the Gregorian calendar (or a Common year starting Arthur Edwin Kennelly ( December 17, 1861 - June 18, 1939) was an Indian American Electrical engineer.

In 1912, the U.S. Congress imposed the Radio Act of 1912 on amateur radio operators, limiting their operations to frequencies above 1. The United States Congress is the bicameral Legislature of the federal government of the United States of America, consisting of two houses The Radio Act of 1912 is a United States federal law that required all seafaring vessels to maintain 24-hour radio watch and keep in contact with nearby ships and coastal radio 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’. Sir Robert Alexander Watson-Watt, FRS FRAeS ( 13 April 1892 &ndash 5 December 1973) is considered by many to be the " Nature is a prominent Scientific journal, first published on 4 November 1869 . 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. Sir Edward Victor Appleton, GBE ( September 6, 1892 – April 21, 1965) was an English Physicist. The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature Lloyd Berkner first measured the height and density of the ionosphere. Lloyd Viel Berkner (born February 1, 1905, in Milwaukee died June 4, 1967, in Washington D 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. John Ashworth Ratcliffe FRS ( 12 December, 1902 &ndash 25 October, 1987) "JAR or Jack" was an influential British Radio Vitaly Ginzburg has developed a theory of electromagnetic wave propagation in plasmas such as the ionosphere. Vitaly Lazarevich Ginzburg (Виталий Лазаревич Гинзбург born October 4 1916 in Moscow) is a Russian theoretical physicist

In 1962 the Canadian satellite Alouette 1 was launched to study the ionosphere. Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page Alouette 1 was Canada 's first satellite and the first satellite operated by a country other than the USSR or the United States. Following its success were Alouette 2 in 1965 and the two ISIS satellites in 1969 and 1971, all for measuring the ionosphere. Alouette 2 was a Canadian research satellite launched at 4h48 UTC on November 29, 1965 by a Thor Agena rocket with Explorer 31 ISIS I and II (International Satellites for Ionospheric Studies were the third and fourth satellites that were launched in a

References

• 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.
• K. Rawer and Y. V. Ramanamurty (eds) (1 January 1986). New Year See also New Year The Ancient Romans began their consular year on January 1st since 153 BC Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar) "International Reference Ionosphere - Status 1985/86". Advances in Space Research 5 (10). ISBN 0-08-034026-1 (Publisher: Pergamon Press), ISSN 0273-1177. An International Standard Serial Number ( ISSN) is a unique eight-digit number used to identify a print or electronic Periodical publication.  

See also

• Geophysics
  • Van Allen radiation belt
• Radio
  • Fading
  • Line-of-sight propagation
  • List of telecommunications transmission terms
  • Ionospheric absorption
• Related
  • Tether propulsion
  • Canadian Geospace Monitoring
  • Pioneer Venus project
  • Nozomi
  • New Horizons
  • Soft gamma repeater
  • TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics)
  • International Geophysical Year
  • Upper Atmospheric Lightning
• Lists
  • List of astronomical topics
  • List of electronics topics

External links

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