Rocket probe observations of electric field irregularities in the polar summer mesosphere

Electric field wave measurements gathered on a sounding rocket flown in the presence of polar mesospheric summer echoes reveal a distinct layer of irregularities between 83–86 km with broadband amplitudes of > 10 mV/m rms. The waves are characterized by bursty, spiky waveforms with lower frequencies (∼ 10 Hz) dominant in the upper portion of the layer near 85 km and broader band emissions, extending to higher frequencies (∼ 1000 Hz) dominant in the lower portion of the layer near 83.5 km. The lower altitudes correspond to a region of weak optical emissions associated with a noctilucent cloud. The waves appear in and around regions where charged/neutral aerosols (1–10 nm) and large electron density depletions were observed. The irregularities likely result from a variety of processes including space charge inhomogeneities, mixed neutral and plasma motions, and complex effects associated with charged aerosols of varying sizes.