Plasma physics is the study of ionized gases, where a significant fraction of the particles are charged, creating a medium that exhibits collective behavior influenced by electromagnetic fields. Plasma is often referred to as the fourth state of matter, alongside solids, liquids, and gases. In a plasma, the thermal energy is sufficient to ionize atoms, resulting in a mixture of positively charged ions and free electrons. This ionization leads to unique properties such as electrical conductivity, response to magnetic fields, and the ability to generate complex, collective phenomena like waves and instabilities. Plasma physics combines elements of fluid dynamics, electromagnetism, and statistical mechanics to describe the behavior of charged particles and fields.

Plasmas are characterized by several key parameters, including the electron and ion densities, temperature, and degree of ionization. The Debye length, which measures the distance over which electrostatic interactions are screened out by the collective response of charges, is a fundamental scale in plasma physics.