We present a geometrical methodology to interpret the periodical light curves of soft gamma repeaters based on the magnetar model and the numerical arithmetic of the three-dimensional magnetosphere model for the young pulsars. The hot plasma released by the starquake is trapped in the magnetosphere, and photons are emitted tangentially to the local magnetic field lines. The variety of radiation morphologies in the burst tails and the persistent stages could be well explained by the trapped fireballs on different sites inside the closed field lines. Furthermore, our numerical results suggest that the pulse profile evolution of SGR 1806–20 during the 2004 December 27 giant flare is due to a lateral drift of the emitting region in the magnetosphere.
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