Ionosphere

The ionosphere is the part of the atmosphere that is ionized by solar radiation. It forms the inner edge of the magnetosphere and has practical importance because it influences high-frequency (HF) (3–30 MHz) radio propagation to distant places on the Earth.

History

In 1899, Nikola Tesla researched ways to utilize the ionosphere to transmit energy wirelessly over long distances. In his experiments, he transmitted extremely low frequencies between the earth and ionosphere, up to what is called the Kennelly-Heaviside Layer (Grotz, 1997). Tesla made mathematical calculations and computations based on his experiments. He predicted the resonant frequency of this area within 15% of modern accepted experimental value. (Corum, 1986) In the 1950s, researchers confirmed the resonant frequency was at the low range 6.8 Hz.

Related Topics:
1899 - Nikola Tesla - Transmit energy wirelessly - Kennelly-Heaviside Layer - 1950s

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Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) using a 400-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. The message received was three dots, 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 work as well as an actual experiments. However, Marconi did achieve transatlantic wireless communications beyond a shadow of doubt in Glace Bay one year later.

Related Topics:
Guglielmo Marconi - December 12 - 1901 - St. John's, Newfoundland - Canada - Poldhu - KHz - Morse code

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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.

Related Topics:
1902 - Oliver Heaviside - 1932 - Arthur Edwin Kennelly

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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.

Related Topics:
1912 - U.S. Congress - Radio Act of 1912 - 1923

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Edward V. Appleton was awarded in 1947 a Nobel Prize for his confirmation of the existence of the ionosphere in 1927. 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.

Related Topics:
Edward V. Appleton - 1947 - Nobel Prize - 1927 - Lloyd Berkner - Maurice V. Wilkes - J. A. Ratcliffe - Vitaly Ginzburg

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In 1962 the Canadian satellite Alouette 1 was launched to study the ionosphere. Following its success were Alouette 2 in 1965 and the two ISIS satellites in 1969 and 1971, all for measuring the ionosphere.

Related Topics:
1962 - Canadian - Alouette 1 - Alouette 2 - 1965 - ISIS - 1969 - 1971

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