Doppler signatures of Halpha flares in AE Aquarii

We present high-speed spectrophotometric observations of the H alpha emission in the exotic cataclysmic variable AE Aqr. Over 10 000 spectra with a sampling rate of similar to 6 s were obtained. The well-known 16.5- and 33-s oscillations were not detected in either the continuum or the line, nor were any quasi-periodic oscillations detected. The H alpha Line shows remarkably complex behaviour, with changes in flux of up to a factor of 3 in a few hours, The line does not act as a single entity - the instantaneous line profile is highly asymmetric and consists of a superposition of emission components that are localized in velocity. We find that during flares the H alpha emission is delayed and decays more slowly than the continuum. The H alpha variations are not linearly correlated with the continuum variations. Examination of the trailed spectrograms and Doppler tomograms reveals no signatures of an accretion disc, but rather supports the idea that mass is being ejected by a propeller mechanism.