Current closure in the pulsar magnetosphere

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: (1) The magnetosphere is everywhere ideal and force free, except above the polar cap and in some finite part of the current sheet; and (2) pairs are produced above the polar cap with multiplicity kappa. We show that a thin region of width delta approximate to 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 centre to the edge of the polar cap. The dissipated electromagnetic energy is approximately equal to 1.5/kappa times the total pulsar spin-down energy loss. Our framework allows to calculate the high-energy emission in terms of the pair multiplicity.