Abstract
PROF. E. V. APPLETON showed in our columns in 1931 the importance of determining the variation, with frequency, of the equivalent path traversed by wireless signals returned from the ionosphere, since such determinations measure the maximum density of ionisation in the regions sounded. The letter from Mr. K. Naismith which we publish in our correspondence columns this week describes work which he carried out in May 1933. We understand that publication was deferred in accordance with an agreement between British and German workers that none of the results of radio work within the programme of the Second International Polar Year should be published until after the end of that year. The letter directs attention to the need for a rapid and more or less completely automatic method for recording the relation between the radio frequency of the pulse signals used and the equivalent path traversed by them in their double journey to and from the ionosphere, at nearly vertical incidence. At the time when the work described was carried out, there were available several methods for the continuous automatic recording of equivalent path against time of day, for a single frequency, but not for the more difficult problem of recording path against frequency.
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Sounding the Ionosphere. Nature 133, 57 (1934). https://doi.org/10.1038/133057a0
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DOI: https://doi.org/10.1038/133057a0
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