Effect of collective propagation of streamers on their parameters

Abstract:

It is important to know accurately the parameters of electric streamer propagation in air, such as their velocity, radius and the maximum field at the tip, because their values directly define the further lightning development. The parameters are dependent on background conditions, which must be carefully accounted for. Even in a uniform constant background electric field, the propagation of a streamer is a very non-stationary process, with propagation parameters strongly dependent on streamer length.

In this work, we investigate theoretically the effects of streamers propagating collectively, e.g., in a streamer corona, so that the field of the neighboring streamers is affecting their propagation. In particular, we show that when the streamers are close to each other, their propagation stabilizes, i.e., the velocity and radius tend to stationary values. This is in contrast with propagation of single streamers, which are shown to accelerate indefinitely in a uniform field, and may be one of possible explanations for the so-called fast streamers observed in thunderclouds.

The methods used include (1) parametric streamer modelling and (2) hydrodynamic simulation. In the recently developed parametric model, we fully describe a streamer by a limited set of parameters. The parameters in this set may be calculated from relations between them, with an extra condition that the streamer corresponds to the most unstable (fastest-growing) solution. In the hydrodynamic numerical simulation, we solve the hydrodynamic equations for electron density and Maxwell equations using finite-difference methods.