Relativistic electron beam injection simulation results are presented from a new interhemispheric transport model, with a spatial domain reaching from 90 km to 90 km in the conjugate ionospheres. A single beam pulse is injected upward at 700 km during the first time step (10-4 s) and allowed to scatter and decay through collisional interactions with neutral particles and the core plasma. The maximum pulse duration for collisional processes to prevail over the wave-beam instabilities is estimated, and the assumed pulse length is well within this limit. For an L=2 field line, the e-folding time of a 5 MeV beam is 265 s, which is much bigger than the bounce period (0.19 s) and comparable to drift period around the Earth. ¿ 1999 American Geophysical Union