THE author of this work believes that radiation pressure on certain small particles in the corona should balance gravitation so closely that a ‘sensitive layer’ exists. If this is disturbed, it will undergo violent motion and probably ejection. The force likely to produce the disturbances is the tidal action due to the planets, and though this is too weak to cause any noticeable motion in the heavier, luminous portion of the sun's gases, nevertheless, as the hydrogen prominences appear at a level comparable in height to the altitude of the ‘sensitive layer’, it is important to seek for some connexion between the disturbances and tidal forces. Only five planets need be considered to contribute anything of importance to the tidal force—Mercury, Venus, Earth, Jupiter and Saturn. Mercury, though very small, must be taken into account because the tidal force varies inversely as the cube of the distance of the planet from the sun; Mars is neglected as its tidal force is only about 3 per cent that of the earth. The five tidal forces are added vectorially, the resultant vector giving the height h of the force wave running round the equator, and the main investigation is carried out on these lines.
Tidal Forces in the Sun's Corona due to Planets
By K. G. Meldahl. Pp. 14 + 7 plates. (Copenhagen: Berlingske Forlag, 1938.) n.p.
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D., M. Tidal Forces in the Sun's Corona due to Planets. Nature 144, 726 (1939). https://doi.org/10.1038/144726a0