  We study the phase dynamics in coupled Josephson junctions describing by
system of nonlinear differential equations. Results of detailed numerical
simulations of charge creation in the superconducting layers and the
longitudinal plasma wave (LPW) nucleation are presented. We demonstrate the
different time stages in the development of the LPW and present results of FFT
analysis at different values of bias current. The correspondence between the
breakpoint position on the outermost branch of current voltage characteristics
(CVC) and the growing region in time dependence of the electric charge in the
superconducting layer is established. The effects of noise in the bias current
and the external microwave radiation on the charge dynamics of the coupled
Josephson junctions are found. These effects introduce a way to regulate the
process of LPW nucleation in the stack of IJJ.
