  In this Letter we propose that coherent radio emission of Crab, other young
energetic pulsars, and millisecond pulsars is produced in the magnetospheric
current sheet beyond the light cylinder. We carry out global and local
two-dimensional kinetic plasma simulations of reconnection to illustrate the
coherent emission mechanism. Reconnection in the current sheet beyond the light
cylinder proceeds in the very efficient plasmoid-dominated regime, and current
layer gets fragmented into a dynamic chain of plasmoids which undergo
successive coalescence. Mergers of sufficiently large plasmoids produce
secondary perpendicular current sheets, which are also plasmoid-unstable.
Collisions of plasmoids with each other and with the upstream magnetic field
eject fast-magnetosonic waves, which propagate upstream across the background
field and successfully escape from the plasma as electromagnetic waves that
fall in the radio band. This model successfully explains many important
features of the observed radio emission from Crab and other pulsars with high
magnetic field at the light cylinder: phase coincidence with the high-energy
emission, nano-second duration (nanoshots), and extreme instantaneous
brightness of individual pulses.
