Solitons in Earth's Dusty Mesosphere

Earth's mesosphere at the altitudes of 80-85 km reveals some layered structures which are known as noctilucent clouds and polar mesosphere summer echoes. These structures are believed to be associated with the presence of a large amount of charged dust or aerosol in the middle atmosphere. The layer of the mesosphere where the dust is present can be called as "the dusty mesosphere". The sign of the charge of dust grains depends on the substance of the dust. As a rule, the grains consist of ice with possible metal impurities. In the case when the part of the metals in the grains is significant, the charge of the dust can be positive. Otherwise for the grains consisting of pure ice the charge is negative. The charge distribution of dust in the grains influences the structure of the dust objects in the middle atmosphere. We investigate the influence of the sign of dust grains on the character of the nonlinear perturbations propagating in the dusty mesosphere. We calculate the solar spectra at the corresponding altitudes. Furthermore, we analyse the material of the dust grains considering the cosmic dust and the water vapor condensation in the dusty mesosphere. We show that the most important nonlinear structures in the dusty mesosphere are dust ion acoustic solitons which correspond to the dust density hump in the case of the grains with positive charge and to the dust density dip in the case of the negative charge. This difference in the properties of the nonlinear structures can serve as a diagnostic means of the plasma of the noctilucent clouds and the polar mesosphere summer echoes. We discuss also the influence of nonlinear structures on the propagation of electromagnetic perturbations in the dust objects of the mesosphere.