In a coplanar plasma display panel the discharges in each pixel are sustained between two parallel electrodes on the same substrate. A third electrode perpendicular to the sustaining electrodes and placed on a facing substrate is used to address the pixel. A self-consistent two-dimensional model of the microdischarge has been used to simulate and study the addressing and sustaining phases in an alternating current coplanar cell. The formation and decay of the transient plasma during the address and sustain discharge pulses are described. The time evolution of the charges on the dielectric surfaces above each electrode is also discussed and the model is used to derive the voltage margins of the address and sustain regimes. © 1999 American Institute of Physics.