Time-dependent screening of the electric field in pulsar discharges and its implications for coherent radio emission

Pulsars produce coherent radio emission, the source of which has remained enigmatic. Recent computational work suggests this emission may be produced in nonstationary pair plasma discharges in the pulsar polar cap, where the pulsar electric field is screened by newly-produced electron-positron pairs, leading to the production of plasma waves which escape from the magnetosphere as radio emission (Philippov et al., Physical Review Letters 2020).  In this talk, we present the physical principles governing the evolution of wave energy in the polar cap's time-dependent, relativistic, collisionless pair plasma, for both linear waves and nonlinear waves. These principles are then used to analytically determine the change in the pulsar polar cap electric field amplitude as it is screened. Finally, we discuss the implications of this model for coherent radio emission and the interpretation of pulsar observations.