We study, analytically and numerically, the dynamics of a matter-wave soliton formed by a Bose-Einstein condensate with an attractive interatomic interaction confined in a one-dimensional harmonic trap and subjected to a flashing weak periodic potential. Within the framework of the Gross-Pitaevski equation, we show that efficient energy transfer to the soliton occurs within two distinct frequency regimes: (a) on resonance with the trapping frequency and (b) on resonance with the internal mode

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... the soliton. We find that the former regime is well described within the soliton-as-particle approximation, while the latter relies on the extended nature of the localized state and involves strong excitations of the width coupled to translational motion.