Estimated Lorentz factor due to the synchrotron cooling effect (γ_cooling) of PL electrons in MAD as a function of radius R. Lines from bottom to top represent MADs whose ﹩{\dot{m}}_{0}=1\times 1{0}^{-4}﹩, 1 × 10⁻⁵, and 1 × 10⁻⁶, respectively. Clearly, the “synchrotron boiler” effect cools most PL electrons, even at accretion rates as low as ﹩{\dot{m}}_{0}\approx 1\times 1{0}^{-5}﹩ (the corresponding X-ray luminosity is L_X ≈ 1.44 × 10³⁷ erg s⁻¹).