  We study the macroscopic quantum tunneling, self-trapping phenomena in two
weakly coupled Bose-Einstein condensates with periodically time-varying atomic
scattering length.
  The resonances in the oscillations of the atomic populations are
investigated. We consider oscillations in the cases of macroscopic quantum
tunneling and the self-trapping regimes. The existence of chaotic oscillations
in the relative atomic population due to overlaps between nonlinear resonances
is showed. We derive the whisker-type map for the problem and obtain the
estimate for the critical amplitude of modulations leading to chaos. The
diffusion coefficient for motion in the stochastic layer near separatrix is
calculated. The analysis of the oscillations in the rapidly varying case shows
the possibilty of stabilization of the unstable Pi-mode regime.
