The Salammboˆ code, which solves the three-dimensional phase-space diffusion equation for the electron radiation belt, was used to explain the dynamic conditions present during a geomagnetic storm. With a simple injection model, we have characterized the dynamic behavior for relativistic electrons in the outer belt. The particles in the range 100 keV--500 keV are diffused throughout the belt, with a shape essentially dependent on the radial diffusion coefficients. Particles with higher energies are ''created'' by acceleration of slower particles near the plasmapause location. The calculated shape of the fluxes in an L-versus time grid for the 1 MeV electrons looks globally like those measured aboard the CRRES satellite. ¿ American Geophysical Union 1996