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The model neutral exosphere of Öpik and Singer for a nonrotating planet is generalized by permitting the corresponding barosphere to rotate uniformly at an angular velocity which may or may not be equal to that of the planet. For this case the velocity-distribution function, satisfying the collisionless Boltzmann equation, is constructed. Then, the density is determined from the distribution and compared with the corresponding result for a nonrotating planet obtained by Öpik and Singer. In addition, the radial and azimuthal fluxes are derived. Based on the result for the azimuthal flux, the point at which exospheric corotation can be said to have broken down is indicated for several conditions. It is shown that in all cases, for a given radius, the density at the equator exceeds the density at the pole. For example, a model terrestrial neutral exosphere of hydrogen, helium, and oxygen has density ratios between the pole and the equator of 0.984, 0.869, and 0.530, respectively, at r = 2R.

The relativistically correct equations of motion for a ’’free’’ electron in a plane electromagnetic wave are written down including radiation damping. Iteration is used to obtain first, the exact solutions neglecting radiation damping, then, corrected solutions including radiation damping. It is seen that without radiation damping the electron will not experience forward acceleration caused by ’’radiation pressure.’’ With radiation damping included, the (constant) acceleration caused by radiation pressure is clearly seen. The effective cross section for the transfer of momentum to the electron is just the Thompson cross section. A ’’Compton formula’’ is obtained that is seen to have the same angular dependence as the ordinary Compton formula. The significance of the Compton formula is then perceived not to lie in its angular dependence, but in its wave independence.

Elastic collisions and rotation inelastic collisions involving quadrupole molecular transitions are important in energy relaxation of electrons in molecular gases. It has been customary in studying the cooling of electrons in a plasma heated by high-frequency waves to characterize this relaxation by the ionospheric G factor. The G factor is first defined in a fundamental way by use of kinetic theory. Then present models for theoretical cross sections for electron collision with O• and N• are used to derive expressions for the G factor in the lower ionosphere. Two models are considered: one uses Gerjuoy-Stein models for both N• and 0'2; the. other uses a Gerjuoy-Stein model for N• and a Geltman-Takayanaki model for O•. Neither O• model has been definitely established experimentally. It is found that temperature dependence of G is critically dependent on the O• model.

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