The structure of the white dwarf accretion disk. The magnetic truncation radius ﹩{R}_{B}^{g}﹩ and the corotation radius R_c are to the right. The disk is not shown to scale. The disk is processed by the Poynting–Robertson (PR) effect from the Roche limit R_R. Once the dust reaches the sublimation temperature, at the location R_s, it is coupled to the magnetic field lines and begins to accrete onto a white dwarf with radius R_⋆. The pollution regions will be two symmetric thin bands on the surface of the white dwarf.