The book details the main issues of physics and chemistry of the middle atmosphere (10-120 km), structure, dynamics, photochemistry, radiation and heat balance, composition (with an emphasis on small components and processes affecting the ozone layers), ionization in the D and E region of the ionosphere. Particular attention is paid to the interaction of different groups of processes (for example, dynamics and photochemistry, changes in the meteorological parameters of the stratomesosphere and the behavior of the lower ionosphere).