Relativistic runaway electron beams driven upward by intense lightning-generated quasielectrostatic (QE) fields undergo intense interactions with the background magnetospheric plasma, leading to rapid nonlinear growth of Langmuir waves. The beam electrons are strongly scattered by the waves in both pitch angle and energy, within one interhemispheric traverse along the Earth's magnetic field lines. While those electrons within the loss cone precipitate out, most of the electrons execute bounce and drift motions, forming detectable trapped curtains of energetic electrons. ¿ 2000 American Geophysical Union