  Interest in air breakdown phenomena has recently been re-kindled with the
advent of advanced virtual prototyping of radio frequency (RF) sources for use
in high power microwave (HPM) weapons technology. Air breakdown phenomena are
of interest because the formation of a plasma layer at the aperture of an RF
source decreases the transmitted power to the target, and in some cases can
cause significant reflection of RF radiation. Understanding the mechanisms
behind the formation of such plasma layers will aid in the development of
maximally effective sources. This paper begins with some of the basic theory
behind air breakdown, and describes two independent approaches to modeling the
formation of plasmas, the dielectric fluid model and the Particle in Cell (PIC)
approach. Finally we present the results of preliminary studies in numerical
modeling and simulation of breakdown.
