  Formation mechanisms of striations along the discharge channel of a
single-filament dielectric barrier discharge (DBD) in argon at atmospheric
pressure are investigated by means of a time-dependent, spatially
two-dimensional fluid-Poisson model. The model is applied to a one-sided DBD
arrangement with a 1.5 mm gap using a sinusoidal high voltage at the powered
metal electrode. The discharge conditions are chosen to mimic experimental
conditions for which striations have been observed. It is found that the
striations form in both half-periods during the transient glow phase, which
follows the streamer breakdown phase. The modelling results show that the
distinct striated structures feature local spatial maxima and minima in charged
and excited particle densities, which are more pronounced during the positive
polarity. Their formation is explained by a repetitive stepwise ionisation of
metastable argon atoms and ionisation of excimers, causing a disturbance of the
spatial distribution of charge carriers along the discharge channel. The
results emphasise the importance of excited states and stepwise ionisation
processes on the formation of repetitive ionisation waves, eventually leading
to striations along the discharge channel.
