  The positron excess observed by PAMELA and then confirmed by AMS 02 has
intrigued the particle physics community since 2008. Various dark matter decay
and annihilation models have been built to explain the excess. However, the
bounds from isotropic gamma ray disfavor the canonical dark matter decay
scenario. We propose a solution to this excess based on the decay of dark
matter particles into intermediate millicharged particles which can be trapped
by the galactic magnetic field. The subsequent decay of the millicharged
particles to electron positron in our vicinity can explain the excess. Since
these particles diffuse out of halo before decay, their contribution to the
isotropic gamma ray background is expected to be much smaller than that in
canonic dark matter decay scenarios. We show that the model is testable by
direct dark matter search experiments.
