Abstract
IN the Joule Memorial Lecture delivered to the Literary and Philosophical Society of Manchester on February 11, Prof. E. V. Appleton said that it was perhaps not inappropriate, in a lecture associated with a great pioneer in thermal measurements, to survey recent advances in our knowledge concerning the temperature of the upper air. Frictional work produces heat, as is well known, and Joule was the first to state the exact nature of this equivalence. An example of the heating process studied by Joule is the flight of a meteor through the atmosphere, in which case the energy of its speed is ultimately transformed into heat and light. But it has been found that electric waves can also heat the atmosphere when they travel through it. Ultra-violet light from the sun, for example, produces a belt of hot air at about the level in the ionosphere (300 km. high) where short wireless waves are reflected. It has also been found that a powerful long-wave wireless station can warm up the Kennelly-Heaviside layer to a very small but still detectable extent. The so-called ‘Luxembourg effect’ noticed by long-distance listeners, who find that they receive a long-wave programme when their receiver is tuned to the medium waves, can be traced to the influence of such a process.
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The Upper Atmosphere. Nature 137, 369–370 (1936). https://doi.org/10.1038/137369a0
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DOI: https://doi.org/10.1038/137369a0