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A Complex Solar Halo

Nature volume 131, pages 613614 (29 April 1933) | Download Citation



A VERY well-developed solar halo of 22° radius with mock sun ring was observed from places in Kent and Sussex on April 14. An excellent description has been received from Mr. R. C. T. Evans and his son, Dr. C. Evans, 10 Eddington Lane, Herne Bay. The 22° halo was observed at about 12.35 p.m. (B.S.T.), and two “bright patches” proceeding not quite radially from the eastern and western sides, at angular positions corresponding roughly with those of the hour hand of a watch at 9.30 and 2.30 o'clock. Shortly afterwards, these bright patches Were observed to form part of a luminous ring which reached northwards to about the position of the pole star (invisible, of course, at the time) but did not cross the region inside the 22° halo. The elevation of the sun must have been nearly 48° at this time and that of the pole star only very slightly greater in this latitude; there seems, therefore, every reason for believing that this ring, which was faint except near the 22° halo, was the mock sun ring, which has the zenith for its centre. The 22° halo showed strong red coloration on the edge nearest to the Bun, and a suspicion of blue towards the outsider—usual features when this halo is strongly developed. There are two points of particular interest about this display. The haloes were seen from near the centre of a large anticyclone, whereas well-developed haloes are more often seen near the outer margin of a depression or even well within the cyclonic vortex. Further, the description from Herne Bay states that the bright patches near the 22° halo, which formed part of the mock sun ring, showed some red colour at the ends nearest to the sun, which is unusual, and they appeared to lie between the observer and one of several flocculent clouds present in the sky which passed across the eastern bright patch. Optical theory suggests that all parts of the haloes were due to a much more elevated veil of cirriform cloud which, on this occasion, was only dense enough to make the blue of the sky appear pale, and that the flocculent clouds should have lain in front of the haloes.

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