This book introduces the theory behind the incoherent scattering of electromagnetic waves (radar waves) by free electrons—a key technique for studying critical parameters of the Earth’s ionosphere. Starting with scattering by statistically independent electrons, including magnetized cases, the book progressively develops a comprehensive model. This framework is extended to include ‘dressed particles’, accounting for long-range Coulomb interactions between charged particles. A consistent approach to incorporating particle collisions is presented, with an example of charge exchange interactions for illustration. Appendices provide essential background material, ensuring the content is accessible to readers.

Based on lectures delivered at the University of Tromsø, Norway, this book is designed for Masters and PhD students. It assumes a basic understanding of electromagnetism and plasma physics, including plasma waves and electrostatic phenomena. Familiarity with kinetic plasma theory and the collisionless Vlasov equation is beneficial but not mandatory.