Evidence for two different structuring and scattering mechanisms and the associated role of aerosols in the polar summer mesosphere

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Abstract
A Super Arcas rocket, MISTI B, was launched as part of the PMSE salvo to measure electron density irregularities using rf and dc probes. Large and small scale structures in the electron density were measured on rocket ascent and descent at the altitudes of 86.5 and 88.5 ±.5 km. Since the rocket apogee was 89 km, the rocket was in the height range 88.5 ±.5 km for 30 seconds giving us an unusual measurement of horizontal structure over a distance of 5.5 km. A power spectrum of the fluctuations for the upper layer gives further evidence that turbulent mixing is an important process in PMSE. The power spectrum of the lower layer, however, gives evidence that this layer is characterized by a form of partial or Fresnel scattering. Both spectra are in excellent agreement with similar analysis of electron fluctuation spectra measured in the same layers on the TURBO‐B rocket flown 12 minutes later and the analysis of CUPRI data by Cho et al., 1993A. Thus two different structuring and scattering mechanisms exist at altitudes only 1 km apart. Using the simultaneous dc and rf probe measurements of electron depletions and sharp gradients in the lower layer, we speculate on the role of aerosols in creating these depletions and gradients.