  We investigate the superconducting lifetime of long current-biased Josephson
junctions, in the presence of Gaussian and non-Gaussian noise sources. In
particular, we analyze the dynamics of a Josephson junction as a function of
the noise signal intensity, for different values of the parameters of the
system and external driving currents. We find that the mean lifetime of the
superconductive state is characterized by nonmonotonic behavior as a function
of noise intensity, driving frequency and junction length. We observe that
these nonmonotonic behaviours are connected with the dynamics of the junction
phase string during the switching towards the resistive state. An important
role is played by the formation and propagation of solitons, with two different
dynamical regimes characterizing the dynamics of the phase string. Our analysis
allows to evidence the effects of different bias current densities, that is a
simple spatially homogeneous distribution and a more realistic inhomogeneous
distribution with high current values at the junction edges. Stochastic
resonant activation, noise enhanced stability and temporary trapping phenomena
are observed in the system investigated.
