Succinctly put, "Collisionless plasmas are weakly coupled, i.e., the coupling between the particles due to collisions is generally negligible, and instead, the long-range collective interactions bind particles together." In other words, the charged particles are mainly affected by the net charge distribution and the magnetic field.Jd1431 said:Hi, I'm trying to understand what determines whether a plasma will be collisionless or collisional. I understand that a diffuse plasma with large mean free path will be collisionless but I don't really understand it from an electromagnetic point of view
A plasma is a state of matter in which atoms are ionized and the resulting particles (electrons and ions) are free to move independently. A plasma is considered collisionless when the particles do not collide with each other, but instead interact through electromagnetic forces.
A plasma becomes collisionless when the density of particles is low enough that the mean free path (the average distance a particle travels before colliding with another particle) is longer than the size of the plasma. This typically occurs at high temperatures and low pressures.
A collisionless plasma behaves differently than a collisional plasma. In a collisionless plasma, collective effects such as plasma waves and instabilities can occur, and the particles can exhibit non-thermal distributions. This can have implications for plasma confinement and energy transport.
There are various experimental and theoretical techniques for studying collisionless plasmas. Some common methods include using particle-in-cell simulations, laser scattering diagnostics, and spectroscopic measurements. Experiments can also be conducted in specialized devices such as magnetic fusion devices or plasma thrusters.
Collisionless plasmas have many practical applications, including plasma processing for semiconductor manufacturing, plasma propulsion for space travel, and plasma medicine for cancer treatment. They are also important for understanding astrophysical phenomena such as solar flares and the dynamics of the interstellar medium.