Significant magnetic field-aligned flows were detected by Voyager 1 during its encounter with Jupiter. We try to understand the origin and dynamics of the field-aligned flow in the presence of a slow corotating convection. We find that the field-aligned flow is a necessary part in the preservation of the magnetodisc geometry and mass conservation in the disc. We further investigate the dynamical origin of the flow on the basis of a phenomenological equation, which indicates that the field-aligned dynamics is likely to be chaotic. ¿ American Geophysical Union 1993