  Current closure in the pulsar magnetosphere holds the key to its structure.
We must determine not only the global electric circuit, but also the source of
its electric charge carriers. We address this issue with the minimum number of
assumptions: a) The magnetosphere is everywhere ideal and force-free, except
above the polar cap and in some finite part of the current sheet; and b) pairs
are produced above the polar cap with multiplicity kappa. We show that a thin
region of width delta ~ r_pc/2 kappa << r_pc along the rim of the polar cap
provides all the charges that are needed in the equatorial and separatrix
electric current sheet. These charges are transferred to the current sheet in a
narrow dissipation zone just outside the magnetospheric Y-point. The maximum
accelerating potential in this region is equal to the potential drop in the
thin polar cap rim, which is approximately equal to 1/kappa times the potential
drop from the center to the edge of the polar cap. The dissipated
electromagnetic energy is approximately equal to 0.5/kappa times the total
pulsar spindown energy loss. Our framework allows to calculate the high energy
emission in terms of the pair multiplicity.
