  The plasma parameters such as electron distribution function and electron
density of three atmospheric-pressure transient discharges namely filamentary
and homogeneous dielectric barrier discharges in air, and the spark discharge
of argon plasma coagulation (APC) system are determined. A combination of
numerical simulation as well as diagnostic methods including current
measurement and optical emission spectroscopy (OES) based on nitrogen emissions
is used. The applied methods supplement each other and resolve problems, which
arise when these methods are used individually. Nitrogen is used as sensor gas
and is admixed in low amount to argon for characterizing the APC discharge.
Both direct and stepwise electron impact excitation of nitrogen emissions are
included in the plasma-chemical model applied for characterization of these
transient discharges using OES where ambiguity arises in the determination of
plasma parameters at specific discharge conditions. It is shown that the
measured current solves this problem by providing additional information useful
for the determination of discharge-specific plasma parameters.
