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Letters to Nature

Nature 325, 699-701 (19 February 1987) | doi:10.1038/325699a0; Received 24 June 1986; Accepted 2 December 1986

Scintillation of a radio source observed through the tail of comet Halley

O. B. Slee*, D. McConnell*, J. Lim† & A. D. Bobra‡

  1. *Division of Radiophysics, CSIRO, PO Box 76, Epping, NSW 2121, Australia
  2. † Department of Mathematics and Physics, Macquarie University, North Ryde, NSW 2113, Australia
  3. ‡Physical Research Laboratory, Ahmedabad 380009, India
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On 29 March 1986 between 16:00 and 23:00 UT we observed the strong compact radio source 1827-360 as the plasma tail of comet Halley swept across the source. We noted the appearance of weak intensity fluctuations during the interval 17:00 to 19:00 UT when the Sun, the comet's nucleus and the radio source were accurately aligned. We interpret this behaviour as the result of diffraction of radio waves by electron-density irregularities in the plasma tail. At a distance 5.4 times 106 km downstream from the cometary nucleus the central part of the plasma tail contained electron density irregularities about 14 times as strong as those in the undisturbed solar wind.