Wave disturbances in sporadic-E-layer parameters at midlatitudes

The paper examines vertical-sounding data on the Es layer collected on days when mesoscale internal gravity waves (IGW) with lambda(z) greater than 10 km were observed at a height of 90 km. A quasi-periodic structure in the variations of the cutoff frequency and the effective height of the Es layer due to the IGW propagation was identified. The analysis indicates that, in the winter, atmospheric waves tend to pass upward through the turbopause from mesospheric heights, whereas, in the summer, they tend to decay at this level, causing turbulence.