  A pin liquid anode DC discharge is generated in open air without any
additional gas feeding to form self-organized patterns (SOPs) on various liquid
interfaces. Axially resolved emission spectra of the whole discharge reveal
that the self-organized patterns are formed below a dark region and are visible
mainly due to the N2 transitions. The high energy N2 (C) level is mainly
excited by the impact of electrons heated by the local increased electric field
at the interface. For the first time, the effect of the liquid type on the SOP
formation is presented. With almost the same other discharge conditions, the
formed SOPs are significantly different from HCl and H2SO4 liquid anodes. The
SOP difference is repeated when the discharge current and gap distance change
for both liquid anodes. The variations of SOP size and discretization as a
function of discharge current and gap distance are discussed and confirm that
different SOPs are formed by the HCl liquid anode from tap water or the H2SO4
liquid anode. A possible explanation is brought up to explain the dependence of
SOPs on the liquid type.
