Aeronomy, Part B discusses the scientific discipline devoted to the study of the composition, movement, and thermal balance of planetary atmospheres. The book presents the comprehensive exposition of the basic processes involved in the aeronomy of the earth's upper atmosphere. It demonstrates the chemical, ionic reactions, and the different collisional interactions involving particles and radiation. The text describes the molecular diffusion and its effects in producing the transition from homogeneous molecular gases of lower atmosphere to the heterogeneous atomic and molecular gases of the upper atmosphere. It also discusses the simple models of the ionospheres. Another topic of interest is the calculations of atmospheric photoionization. The section that follows describes the satellite and external hyperbolic particles. The book will provide valuable insights for engineers, scientists, students, and researchers in the field of space science.