Numerical simulation of the Ar plasma jet in the cold N2-02-Ar mixture under atmospheric pressure is performed. The TVD scheme is applied to
solve the conservation equations of mass, momentum and energy for a compressible plasma flow. Origination, development and dynamics of the transonic plasma flow
exiting the nozzle are studied. Peculiarities of the transition of the plasma jet into the steady-state regime are discussed. It is shown that the initial stage of the
development of the transonic plasma jet in air is a complex phenomenon and the transition period into the steady-state mode takes about 20 ms. The effect of short-term
variations of velocity and temperature at the nozzle exit on the evolution of gasdynamic fields in the steady-state plasma jet is studied as well. The inlet fluctuations of the above parameters on ± 20% are assumed. It is shown that the variations of temperature and velocity near the nozzle exit don't follow instantly their fluctuations at the inlet. The length of the potential core of the plasma jet is strongly effected by the above fluctuations.