Plasma physics is the study of ionized gases. It is the branch of physics that deals with matter once in the plasma phase. The plasma phase is the fourth state of matter after the gaseous state. The electrons float freely and separate from their nucleons. This property allows plasma to be very reactive to electric and magnetic fields. It is believed among physicists that plasma is the most abundant material in the universe.
Plasma is described as an electrically neutral medium of positive and negative particles. Although these particles are unbound but are not 'free'. When the charges move they generate electrical currents and magnetic fields. This affects the other fields surrounding the plasma. Plasma has a sizable temperature and density ranges and therefore can be used in many applications.
Although 99% of the universe is made up of plasma, most is not found on earth. The environment that supports life is not conductive to naturally occurring plasma. Although plasma may not be naturally occurring on earth, we use it every day in the application of fire, lightning and light from computer screens. Plasma physics and harnessing the properties of plasma is extremely useful.
Studying and understanding plasmas are difficult under normal earth conditions. Much of the understanding has come from controlled nuclear fusion and fusion power experiments. Physicists have found three types of plasma: artificially produced, terrestrial plasmas and space and astrophysical plasmas. Plasma is useful due to its very high electrical conductivity property. Plasma theory, plasma interactions with waves and beams, Coulomb collision, Northern and Southern lights, plasma chemistry, plasma processing, dusty plasmas, plasma-based weaponry, ion thruster, non-thermal plasma, plasma acceleration and plasma medicine are examples of areas of active research involving plasma.