Two-dimensional long pulse calculations of electron layer formation in cross microwave beams in low pressure air

Summary Form only given, as follows. Laboratory chamber experiments in low-pressure (0.1-10 torr) air with long-pulse (100-600-ns), 2.856-GHz crossed microwave beams formed by reflection of a single beam from an inclined metal plate have shown that multiple, luminous electron density layers form sequentially in time toward the source of the incident beam. To model this experiment, a two-dimensional, long-pulse electron fluid computer code has been developed. Initially, the electron evolution in the rectangular, x-y space transverse to the driving E/sub z/ microwave field is described by a convective continuity equation. The convection is approximated by electric drift and thermal diffusion terms in the x and y directions. After the peak electron density has increased to a few percent of the critical density (10/sup 17/ m/sup -3/ at 2.856 GHz), the initial electrostatic equations are replaced by a new set. This features a nonconvective continuity equation, in which drift and diffusion are ignored but ionization is retained, and a harmonic, slowly varying envelope approximation to the wave equation for the driving field. This wave equation appears as two coupled diffusion equations for the real and imaginary parts of the driving field. Calculations have been carried out at 1-torr pressure with a linearly ramped pulse, which reaches a plateau value of 0.159 MV/m at 80 ns.<>