Streamers in air splitting into three branches

TL;DR

This study systematically investigates positive air streamers, revealing that about 1 in 200 branches split into three, especially in thicker streamers, with consistent total cross-sectional surface area before and after branching.

Contribution

First systematic analysis of three-way branching in positive air streamers, providing quantitative data on branching frequency and conditions.

Findings

Approximately 0.5% of branching events are three-way splits.

Three-way branching occurs more often in thicker streamers.

Total streamer cross-sectional area remains roughly constant before and after branching.

Abstract

We investigate the branching of positive streamers in air and present the first systematic investigation of splitting into more than two branches. We study discharges in 100 mbar artificial air that is exposed to voltage pulses of 10 kV applied to a needle electrode 160 mm above a grounded plate. By imaging the discharge with two cameras from three angles, we establish that about every 200th branching event is a branching into three. Branching into three occurs more frequently for the relatively thicker streamers. In fact, we find that the surface of the total streamer cross-sections before and after a branching event is roughly the same.