Cellular atmospheric waves in the ionosphere and troposphere

Abstract

Consideration of horizontally travelling disturbances of electron densities in the F$_{2}$ region of the ionosphere suggests that they are identical with the supposed vertically travelling disturbances discovered by Wells, Watts & George (1946). They appear to be due to horizontally travelling atmospheric cellular waves of the type first investigated by Lamb. The theory of such waves is developed to include wind with linear vertical shear, special attention being paid to the conditions of bounding by temperature gradients. It is found that such waves appear to be the cause of the microbarometric oscillations long known in the troposphere. The theory of these is worked out in some detail, and an explanation found for Johnson's discovery that these oscillations have periods agreeing closely with Brunt's natural period of oscillation of a small element of atmosphere. In the ionosphere, the earth's magnetic field profoundly affects the observed motions of ionization in the F$_{2}$ region, leading to a height gradient in the phase of these oscillatory motions. This gradient makes horizontally travelling disturbances appear to have a vertical component of motion, thus simulating vertically moving electron clouds. The bounding conditions for these cells in the F$_{2}$ region appear to necessitate a value for $\gamma $, the ratio of specific heats of air, considerably less than 1$\cdot $4.