Banded electron structures in energy-time spectrograms have been observed in the inner magnetosphere concurrent with a sudden relaxation of geomagnetic activity. In this study, the formation of these banded structures is considered with a global, bounce-averaged model of electron transport, and it is concluded that this structure is a natural occurrence when plasma sheet electrons are captured on closed drift paths near the Earth followed by an extended period of quiet time for more than a day. These bands do not appear unless there is capture of plasma sheet electrons; convection along open drift paths making one pass around the Earth do not have time to develop this feature. The separation of high-energy bands from the injected population due to the preferential advection of the gradient-curvature drift creates spikes in the energy distribution above a keV, which overlap to form a series of bands in energy. The lowest band is the bulk of the injected population in the sub-keV energy range. Using the Kp history for an observed banded structure event, a cloud of plasma sheet electrons is captured and the formation of their distribution function is examined. ¿ 1998 American Geophysical Union