  We study the dynamics of a magnetically trapped Bose-Einstein condensate in
the presence of an external electromagnetic field coupling trapped, untrapped
and antitrapped Zeeman sublevels. For large condensates an approximate
analytical solution of the coupled Gross-Pitaevskii equations is given in the
regime of strong outcoupling. The theory is developed for the cases of
rf-outcoupling within a hyperfine manifold of states, micowave-outcoupling
connecting states in two different hyperfine manifolds, and Raman outcoupling.
