Measurements of electron fluxes were made using five detectors flown on a sounding rocket into an aurora. Three of the detectors measured fluxes in energy bands about 4, 7, and 10 kev, while two Geiger tubes measured electrons above 50 kev. The time resolution was about one millisecond. The fluxes were analyzed to give a spectrum, and auto-correlations and cross-correlations were performed to find modulations and time lags in modulations among the fluxes of different energy levels. Modulations with periods of about .05 second, .065 second, and .10 second were found with time lags of less than 10 milliseconds between 4 and 10 kev electron fluxes. No such spectral studies of periodicities have been made previously. If the time lags are purely of temporal origin, the distance from the detectors to the source of modulation is calculated to be less than about 1,000 kilometers. The nature of possible modulation mechanisms is analyzed, and the implications to auroral theories discussed.