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A study of 1963 VLF data from Eights, Antarctica, verified that triggering of artificial magnetospheric noise by Morse-code dots at 14.7 kHz occurs rarely by comparison to triggering by dashes. In the few cases (∼0.3% of all runs) when dots were found to trigger noise, this occurred during strong triggering by dashes. On spectrograms, the dot-produced noises were in each case of a simple falling-tone form.
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S. Lasch (1969) studied this question.
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