  The equatorial current sheet in pulsar magnetospheres is often regarded as an
ideal site for particle acceleration via relativistic reconnection. Using 2D
spherical particle-in-cell simulations, we investigate particle acceleration in
the axisymmetric pulsar magnetosphere as a function of the injected plasma
multiplicity and magnetization. We observe a clear transition from a highly
charge-separated magnetosphere for low plasma injection with little current and
spin-down power, to a nearly force-free solution for high plasma multiplicity
characterized by a prominent equatorial current sheet and high spin-down power.
We find significant magnetic dissipation in the current sheet, up to 30% within
5 light-cylinder radii in the high-multiplicity regime. The simulations
unambiguously demonstrate that the dissipated Poynting flux is efficiently
channeled to the particles in the sheet, close to the Y-point within about 1-2
light cylinder radii from the star. The mean particle energy in the sheet is
given by the upstream plasma magnetization at the light cylinder. The study of
particle orbits shows that all energetic particles originate from the boundary
layer between the open and the closed field lines. Energetic positrons always
stream outward, while high-energy electrons precipitate back towards the star
through the sheet and along the separatrices, which may result in auroral-like
emission. Our results suggest that the current sheet and the separatrices may
be the main source of high-energy radiation in young pulsars.
