  One of the most intriguing discoveries made by the Swift satellite is the
flaring activity in about half of the afterglow lightcurves. Flares have been
observed on both long and short duration GRBs and on time scales that range
from minutes to ~1 day after the prompt emission. The rapid evolution of some
flares led to the suggestion that they are caused by late central engine
activity. Here, I propose an alternative explanation that does not need
reviving of the central engine. Flares can be powered by delayed magnetic
dissipation in strongly magnetized (i.e. with initial Poynting to kinetic flux
ratio $\simmore 1$) ejecta during its deceleration due to interaction with the
external medium. A closer look at the length scales of the dissipation regions
shows that magnetic dissipation can give rise to fast evolving and energetic
flares. Multiple flares are also expected in the context of the model.
