ELECTRON SHOCK-WAVES MOVING INTO AN IONIZED MEDIUM

The propagation of electron driven shock waves has been investigated b y employing a one-dimensional, three-component fluid model. In the flu id model, the basic set of equations consists of equations of conserva tion of mass, momentum, and energy, plus Poisson's equation. The wave is assumed to be a shock front followed by a dynamical transition regi on. Following Fowler's (1976) categorization of breakdown waves, the w aves propagating into a preionized medium will be referred to as Class II Waves. To describe the breakdown waves, Shelton and Fowler (1968) used the terms proforce and antiforce waves, depending on whether the applied electric field force on electrons was with or against the dire ction of wave propagation. Breakdown waves, i.e., return strokes of li ghtning flashes, therefore, will be referred to as Antiforce Class II waves. The shock boundary conditions and Poisson's equation for Antifo rce Class II waves are different from those for Antiforce Waves. The u se of a newly derived set of boundary conditions and Poisson's equatio n for Antiforce Class II waves allows for a successful integration of the set of fluid equations through the dynamical transition region. Th e wave structure, i.e., electric field, electron concentration, electr on temperature, and electron velocity, are very sensitive to the ion c oncentration ahead of the wave.