Localized structures of nanosize charged dust grains in Earthʹs middle atmosphere

The Earthʹs middle atmosphere at altitudes of 80–95 km exhibits layered phenomena known as noctilucent clouds and polar mesosphere summer echoes. These structures are believed to be associated with the presence of large quantities of charged dust or aerosol particles. The sign of the charge depends on the material composition of the latter as well as the environment. The grains are normally composed of ice together with possible metallic impurities. Particles of pure ice are always charged negatively, but if the metal content is sufficiently high, they can become positive. The characteristics of self-organized structures on the dust acoustic time scale depend strongly on the sign of the charge, and the structures can appear as either electron (ion) density humps or dips. Such a physical distinction can be used for the identification and diagnostics of noctilucent clouds and polar mesosphere summer echoes.