Societies and Academies

Abstract

LONDON Royal Society, March 19. D. F. MABTYN and O. O. PULLEY: The temperatures and constituents of the upper atmosphere. Radio measurements of the heights and electron densities of the ionised regions indicate considerable cooling of the upper atmosphere during the night. The absolute temperatures between the E and F regions of the ionosphere are found, from consideration of the electron collision frequencies, to reach values of the order 1,000° K. in both summer and winter daytime. From the observed rate of cooling at night, considerable water vapour is present in the ionosphere, an average concentration being one part in 6,000 by volume. The high temperatures found are attributed mainly to ozone, in concentration of 1 part in 104. The ionisation densities in the E and F regions are correlated directly, and the height of the F region indirectly, with the barometric pressure at the ground. This correlation is attributed to the temperature changes in the ionosphere occasioned by changes in ozone concentration. The attachment of electrons to neutral particles is the main process by which free electrons are removed from the ionised regions. As regards temperatures below 100 km., a maximum is found at 60 km., and a minimum of 160° K., at 82 km. Noctilucent clouds are found to be formed of ice crystals. P. I. DEE and C. W. GILBERT: The disintegration of boron into three a-particles. The common mode of disintegration is into two particles which proceed at angles of 150° to 180° relatively to one another, the third particle receiving little energy. A theoretical picture of the process, involving the existence of an unstable JBe nucleus, of very short life, explains the main features of the distribution of energy among the particles emitted in this process and also in the similar three-body disintegration of boron under deu-teron bombardment. The value 8.7 ± 0-2 × 106e.v. was obtained for the total energy release in the first reaction.