ionosphere and its implification of communication

8/6/2019 Ionosphere and Its Implification of Communication

1/13

Presented By: 31014 LAC Perera MMB


2/13

TheThe ionosphereionosphere is a part of the upperis a part of the upperatmosphere, comprising portions of theatmosphere, comprising portions of themesosphere ,mesosphere , thermospherethermosphere and exosphere ,and exosphere ,

distinguished because it is ionizeddistinguished because it is ionized by solarby solarradiation. It plays an important part inradiation. It plays an important part inatmosphericatmospheric electricityelectricity and forms the inner edgeand forms the inner edgeof the magnetosphere. It has practical importanceof the magnetosphere. It has practical importancebecause, among other functions, it influencesbecause, among other functions, it influencesradio propagationradio propagation to distant places on the Earthto distant places on the Earth.

WHAT IS IONOSPHERE


3/13

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 wasconducting wireless telegraphy experiments transmitting signals from

Pikes Peak to Paris . Tesla's diary contains explanations of his experiments

concerning the ionosphere. Guglielmo Marconi received the first trans-Atlantic radio signal on

December 12, 1901, in St. John's, Newfoundland (now in Canada) using a152.4 m (500 ft.) kite-supported antenna for reception. The transmitting

station in Poldhu, Cornwall used a spark-gap transmitter to produce asignal with a frequency of approximately 500 kHz and a power of 100

times more than any radio signal previously produced

HISTORY OFHISTORY OF IONOSPHEREIONOSPHERE


4/13

When a radio wave reaches the ionosphere, the electric

field in the wave forces the electrons in the ionosphereinto 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 theneither be lost to recombination or will re-radiate the

original wave energy. Total refraction can occur when thecollision frequency of the ionosphere is less than the radio

frequency,

MECHANISMOF REFRACTIONMECHANISMOF REFRACTION

IONOSPHEREIONOSPHERE


5/13

D layer

E layer

E s

F layer

Ionosphere model

THERE ARE 5 LAYERSTHERE ARE 5 LAYERS


6/13

At night the F layer is the only layer of significant ionization present, whilethe ionization in the E and D layers is extremely low. During the day, the Dand E layers become much more heavily ionized, as does the F layer, whichdevelops an additional, weaker region of ionization 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 IONOSPHERIC LAYERSTHE IONOSPHERIC LAYERS


7/13

The D layer is the innermost layer, 60 km to 90 km above the surfaceof the Earth. Ionization here is due to Lyman series-alpha hydrogenradiation at a wavelength of 121.5 nanometer (nm) ionizing nitricoxide (NO). In addition, with high Solar activity hard X-rays(wavelength < 1 nm) may ionize (N2, O2). During the night cosmic

rays produce a residual amount of ionization. Recombination is highin the D layer, the net ionization effect is low, but loss of wave energyis great due to frequent collisions of the electrons (about tencollisions every m sec). As a result high-frequency (HF) radio wavesare not reflected by the D layer but suffer loss of energy therein. This

is the main reason for absorption of HF radio waves, particularly at10 MHz and below, with progressively smaller absorption as thefrequency gets higher. The absorption is small at night and greatestabout midday. The layer reduces greatly after sunset; a small partremains due to galactic cosmic rays. A common example of the Dlayer in action is the disappearance of distant AM broadcast band

stations in the daytime

D LAYERD LAYER


8/13

The E layer is the middle layer,90 km to 120 km above the surface ofthe Earth. Ionization is due to soft X-ray (1-10 nm) and far ultraviolet(UV) solar radiation ionization of molecular oxygen (O2). Normally, atoblique incidence, this layer can only reflect radio waves havingfrequencies lower than about 10 MHz and may contribute a bit to

absorption on frequencies above. However during intense Sporadic Eevents the E s layer can reflect frequencies up to 50 MHz and higher .The vertical structure of the E layer is primarily determined by thecompeting effects of ionization and recombination. At night the Elayer rapidly disappears because the primary source of ionization is

no longer present. After sunset an increase in the height of the Elayer maximum increases the range to which radio waves can travelby reflection from the layer

EE LAYERLAYER


9/13

The Es' layer (sporadic E-layer) is characterized by small, thin cloudsof intense ionization, which can support reflection of radio waves,rarely up to 225 MHz Sporadic-E events may last for just a fewminutes to several hours. Sporadic E propagation makes radioamateurs very excited, as propagation paths that are generally

unreachable can open up. There are multiple causes of sporadic-Ethat are still being pursued by researchers. This propagation occursmost frequently during the summer months when high signal levelsmay be reached. The skip distances are generally around 1000 km(620 miles). Distances for one hop propagation can be as close as

900 km [500 miles] or up to 2500 km (1,400 miles). Double-hopreception over 3500 km (2,000 miles) is possible.

Es'Es' LAYERLAYER


10/13

The F layer or region, also known as the Appleton layerextends from about 200 km to more than 500 km abovethe surface of Earth. It is the densest point of theionosphere, which implies signals penetrating this layer

will escape into space. Beyond this layer is the topsideionosphere. Here extreme ultraviolet (UV, 10100 nm)solar radiation ionizes atomic oxygen. The F layer consistsof one layer at night, but during the day, a deformationoften forms in the profile that is labeled F1. The F2 layer

remains by day and night responsible for most sky wavepropagation of radio waves, facilitating high frequency(HF, or shortwave) radio communications over longdistances.

FF LAYERLAYER


11/13

An IONOSPHERIC model is a mathematical description of

the ionosphere as a function of location, altitude, day ofyear, phase of the sun spot cycle and geomagneticactivity. Geophysical, the state of the IONOSPHERIC

plasma may be described by four parameters: electrondensity, electron and ion temperature and, since several

species of ions are present, ionic composition. Radiopropagation depends uniquely on electron density

IONOSPHERICIONOSPHERIC MODELMODEL


12/13

DX communication, popular among amateurradio enthusiasts, is a term given tocommunication over great distances. Thanks to

the property of ionized atmospheric gases torefract high frequency (HF, or shortwave) radiowaves

IONOSPHEREIONOSPHERE


13/13

ionosphere and its implification of communication

Documents