Simulations of synchrotron emission from relativistic electrons trapped in Jupiter's magnetic field are used to evaluate the energetic electron distribution of the Divine-Garrett Jupiter radiation belt model at radial distances less than 4 Jovian radii. The fundamental characteristic of synchrotron emission, narrow beaming from gyrating electrons, provides the basis for constraints on both the magnetic field and the distribution of particles in the inner magnetosphere. A comparison between model results and observations is presented. The results suggest the Divine Garrett model significantly underestimates the number of relativistic electrons (> 1 MeV) present in Jupiter's inner magnetosphere. The results also indicate that the pitch angle distribution of relativistic electrons in the Jovian radiation belts is different than assumed in the Divine-Garrett model. These results have important implications for the development of self-consistent models of Jupiter's magnetosphere and the planning of future missions requiring close flybys of Jupiter. ¿ 2001 American Geophysical Union