Branching of negative streamers in free flight

TL;DR

This paper demonstrates through improved simulations that negative streamers in high homogeneous fields can spontaneously branch from a single electron, showing that branching is a fundamental behavior not dependent on initial seed size.

Contribution

It shows that negative streamers can branch spontaneously from a single electron, extending previous findings and highlighting the intrinsic instability leading to branching.

Findings

Streamers branch spontaneously from a single electron.

Branching occurs after a shorter propagation distance in narrow streamers.

Branching is driven by a Laplacian instability, not stationary modes.

Abstract

We recently have shown that a negative streamer in a sufficiently high homogeneous field can branch spontaneously due to a Laplacian instability, rather than approach a stationary mode of propagation with fixed radius. In our previous simulations, the streamer started from a wide initial ionization seed on the cathode. We here demonstrate in improved simulations that a streamer emerging from a single electron branches in the same way. In fact, though the evolving streamer is much more narrow, it branches after an even shorter propagation distance.