Nature 325, 699 - 701 (19 February 1987); doi:10.1038/325699a0

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

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

^*Division of Radiophysics, CSIRO, PO Box 76, Epping, NSW 2121, Australia
^† Department of Mathematics and Physics, Macquarie University, North Ryde, NSW 2113, Australia
^‡Physical Research Laboratory, Ahmedabad 380009, India

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 5.4 10⁶ 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.

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