Convection in a Martian magnetosphere

Data from the Mars 2 and 3 orbiters suggest the existence of a Martian magnetosphere. We wish to point out that the Martian magnetosphere would probably be one in which the drag on magnetic field lines tied to a highly conducting day side ionosphere greatly inhibits the line-merging rate at the magnetopause. We deduce a maximum merging speed that is 1-2 orders of magnitude less than the local Alfven speed. We also conclude that the magnetospheric magnetic fields caused by ionospheric currents should be comparable to those due to the small intrinsic dipole moment implied by the spacecraft data. The shape and the size of the magnetosphere are likely to be highly variable.