The ionopause current layer at Venus

The results of recent theoretical models for the magnetic field in the ionosphere of Venus are reviewed, with special attention given to the 1D MHD model of Shinagawa and Cravens (1989) and the 2D kinematic dynamo model of Cravens et al. (1990). The results are used to examine the behavior of the ionopause, and it is suggested that the sensitivity of horizontal plasma transport to the presence of a magnetic field and the convergence of the vertical flow explain the narrowness of the Venus ionopause. During high solar wind dynamic pressure conditions, ion-neutral friction also plays an important role in determining the thickness of the ionopause.