Diffusion of heavy ions in the solar corona

The steady‐state diffusive motion of ionized atoms (more massive than hydrogen) in the solar corona has been investigated theoretically, with special emphasis on relating the flow velocity and density of these ions to the flow properties of the ionized hydrogen background. The basic approach taken in this study was to regard the ions as ‘test particles’ interacting with the background electrons and protons; an explicit form of the momentum equation for the ions was derived that contained, as parameters, the density, the velocity, and the temperature of the electrons and protons. These parameters were assumed to be unperturbed by the addition of the ions and were obtained from two models of a simpler corona that consists of ionized hydrogen only: the model of E. N. Parker and the model of P. A. Sturrock and R. E. Hartle. The momentum equation was combined with the equation for conservation of mass and was solved to obtain, as a function of distance from the sun, the flow velocity and density for certain representative species of ions. It was found that the ions diffuse away from the sun with velocities somewhat lower than the velocity of the background, and that their relative abundance increases gradually and slowly with height.