Positive streamer between parallel plate electrodes in atmospheric pressure air

The results of a two-dimensional simulation of a cylindrically symmetric positive streamer in atmospheric pressure air between parallel plate electrodes are reported. A hydrodynamic diffusion-drift model was used. The results show that the streamer radius and velocity grow exponentially in time. We have found that the main parameter which governs streamer propagation is the width of the space charge front R(rho). It is shown that: (i) the field at the tip of the streamer is equivalent to the field of a charged ball of radius R(rho); and (ii) the streamer velocity is proportional to R(rho), as previously predicted by Loeb [1]. The mechanism of streamer propagation is discussed. It is shown that positive streamer advancement occurs due to avalanche multiplication of primary photoelectrons in the narrow layer of the width R(rho) ahead of the streamer. The energy delivered by the power supply is calculated. This energy accumulates as electrostatic energy of the space charge envelope around streamer channel. The energy increases exponentially in time and reaches similar or equal to 10(2) J when the streamer radius is about 20 cm.