What is collective behavior in plasma physics?

Answer 1

The definition teaches us: plasma is a set of quasi-neutral particles with free electric charge carriers, which behave collectively. Let us analyze each part of this definition. The most important part is that free electric charge carriers are found in the plasma state of matter. Atoms are at least partially ionized. The degree of ionization does not have to be too large, if the size of the plasma formation is big enough. Precisely a plasma is different from a gas in that there are free carriers of charge in the former. A plasma is conductive and reacts strongly to electric and magnetic fields. The second quality is its quasi-neutrality. Let us assume a certain volume, which microscopically shows in average the same quantity of positive and negative particles. Seen from the outside, the plasma behaves as if it were a fluid without charge (liquid or gas). The demanding of quasi-neutrality excludes the beams of charged particles from the definition of plasma. The last part of the definition of plasma is its collective behaviour. With this it is understood that plasma as a whole is capable of processes that generate electric and magnetic fields to which plasma can react in turn. The plasma definition does not include the beams of charged particles since they do not fulfill the requirement of quasi-neutrality. Neither are included the very weekly ionized gases, like the flame of a candle (they do not fulfill the requirement of collective behaviour). The plasma concept was used for the first time by Irwing Langmuir(1881-1957).

Answer 2

plasma is many particle system if we apply force on a single particle then we see this force effect on all the particles of system, be like if we see 20 student that are sitting in the classroom, u push a single student and all other students fell the same force that applied on a single one ,in actual this phenomena is not possible but in the case of ideal plasma this will held.