On ion harmonic structure in auroral zone waves: The effect of ion conic damping of auroral hiss

Several low‐altitude auroral wave observations exhibiting ion harmonic frequency structure have been reported. We present here recent S3‐3 wave and particle data that illustrate examples of ion harmonic structure in auroral hiss and the associated energetic ion distributions. Such harmonic features have previously been attributed to either hot ion absorption or emission processes. We model the observed ion conic distributions to evaluate their effect on auroral hiss near the lower hybrid resonance frequency where harmonic features are seen. The calculations indicate that resonant ion damping of auroral hiss can indeed account for this distinct class of observed harmonic feature. The concomitant heating of the ion tail, however, appears insufficient to significantly energize the ion distribution.