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Two stream instability
The two-stream instability is a very common instability in plasma physics. It can be induced by an energetic particle stream injected in a plasma, or setting a current along the plasma so different species (ions and electrons) can have different drift velocities. The energy from the particles can lead to plasma wave excitation.
Additional recommended knowledge
Consider a cold, uniform, and unmagnetized plasma, where ions are stationary and the electrons have velocity , that is, the reference frame is moving with the ion stream. Let the electrostatic waves be of the form:
The two stream instability can be thought of as the inverse of Landau damping, where the existence of a greater number of particles that move slower than the wave phase velocity vph as compared with those that move faster, leads to an energy transfer from the wave to the particles. In the case of the two stream instability, when an electron stream is injected to the plasma, the particle's velocity distribution function has a "bump" on its "tail". If a wave has phase velocity in the region where the slope is positive, there is a greater number of faster particles (v > vph) than slower particles, and so there is a greater amount of energy being transferred from the fast particles to the wave, giving rise to exponential wave growth.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Two_stream_instability". A list of authors is available in Wikipedia.|