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Landau damping is a type of damping of longitudinal waves (pressure waves such as sound waves) that can occur in a plasma sufficiently thin that collisions are rare (the term collision indicating particles passing near enough to each other that their velocity is substantially changed, and damping meaning some mechanism that tends to weaken the waves). In such a plasma, the Coulomb force between the separated particles is generally small and one might presume it is insignificant. But for any particles with a velocity close to that of the waves, the combination of these forces from wave's oscillating particles tend to carry these traveling particles along, tending to synchronize their speed with that of the wave. Under a typical distribution of velocities (Maxwell-Boltzmann distribution), more particles have a velocity slightly slower than the wave than slightly faster, and the net kinetic energy of the particles that are syncing with the wave increases, the difference drawn from the wave's energy. Lev Davidovich Landau worked out the mathematics of such damping in the 1940s. The principles have been borrowed to characterize some stellar dynamics phenomena, in which case the relevant force (between the stars) is gravity.