A more precise and definitive relation between diffuse auroras and their particle source region was determined by examining simultaneously the particle observations at the geosynchronous orbit and the auroral display as well as the auroral electron precipitations near its field line conjugate observed by the polar-orbiting DMSP 32 satellite. It is found that the spectral shape and differential fluxes of precipitated auroral electrons of diffuse auroras are very similar, and sometimes almost identical, to those of the trapped plasma sheet electrons located simultaneously in the conjugate magnetospheric equator. The characteristics of auroral electron precipitations are determined by the particle features in the conjugate magnetospheric equator, and diffuse auroras are produced by the direct dumping of the plasma sheet electrons.