  We investigate the low-energy dynamics of two coupled anisotropic
Bose-Einstein condensates forming a long Josephson junction. The theoretical
study is performed in the framework of the two-dimensional Gross-Pitaevskii
equation and the Bogoliubov-de Gennes formalism. We analyze the excitation
spectrum of the coupled Bose condensates and show how low-energy excitations of
the condensates lead to multiple-frequency oscillations of the atomic
populations in the two wells. This analysis generalizes the standard bosnic
Josephson euqation approach. We also develop a one-dimensional hydrodynamic
model of the coupled condensates, that is capable to reproduce the excitation
spectrum and population dynamics of the system.
