Theoretical considerations indicate that auroral electrons may be modulated by an electrostatic wave generated by instabilities in the ionosphere. A high time resolution (HTR) experiment has been designed to detect such variations and covers the frequency ranges of 0--2.5 kHz and 230 kHz to 9.9 MHz. The energy range sampled is 4--6 keV, and the pitch angle coverage is designed to be from 0¿ to 180¿. The results of the experiment set an upper limit of approximately 5% on the electron modulations in the appropriate frequency ranges and establish the necessity for high-intensity fluxes before this upper limit can be lowered. The experiment was launched on a Nike Tomahawk rocket on the evening of March 14, 1974, and the HTR operated as expected from lift-off. Fluxes peaked at a few times 107 el/cm2 s sr keV during the brightest part of the arc. No modulation was observed in the high-frequency range, a finding which is consistent with the stabilization of the plasma by the low flux of energetic electrons. Suspected modulation around 2 kHz was observed, but no event is of sufficiently long duration or of sufficiently high power level to be defined unequivocally as real electron modulation. The suspected modulation is not confined to any single pitch angle range and is not associated with the high flux gradients (where modulation may be expected) at the northern and southern edges of the arc.