Electric-Field-Induced Anisotropies in an Inhomogeneous Plasma

It is shown on the basis of the Boltzmann equation that in the absence of a dc magnetic field, an electric field alone can produce anisotropies in electron diffusion and conductivity in a weak inhomogeneous plasma. These anisotropies have their origin in the ac component of the electron density resulting from the interaction between the electric field and electron density gradients. Electron diffusion is reduced in the direction of the field, while the induced ac current acquires an additional component in the direction of the gradient of the ac electron density. This component will in general lie in a direction different from that of the exciting field. Although these effects are usually small, they may become significant under suitable circumstances.