Generation mechanism of polar mesosphere summer echoes

A generation mechanism of short‐scale charge density fluctuations is considered, which is based on the interaction between charged aerosol particles and an up drafting airflow. The mechanism is analogous to that of the resistive beam‐plasma instability. It is shown that the most favorable conditions for the instability are realized at the height of mesospheric temperature minimum, h ∼ 87 km, in the regions where the electron density is relatively low and heavy ions are predominant. An attempt is undertaken to apply this mechanism for explanation of some types of polar mesosphere summer echoes (PMSE), which correlate with atmospheric convective cells and intense gravity waves. The instability threshold can be achieved if an ionized air component includes a group of charged aerosol particles with the radius ra = 0.2 μm and charge number |Z| ∼ 103, or two groups of light (ra1 ∼ 10−2–10−3 μm, |Za1| ∼ 1) and heavy (ra2 ∼ 0.1 μm, |Za2| ∼ 10–102) particles with a small addition of electrons and ions.