Ion acoustic wave

An ion acoustic wave is a longitudinal oscillation of the ions (and the electrons) in an unmagnetized plasma or in a magnetized plasma parallel to the magnetic field. The waves are dispersionless with a speed given by

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In this equation k is Boltzmann's constant, M is the mass of the ion, Z is its charge, T_e is the temperature of the electrons and T_i is the temperature of the ions. Normally γ_e is taken to be unity, on the grounds that the thermal conductivity of electrons is large enough to keep them isothermal on the time scale of ion acoustic waves, and γ_i is taken to be 3, corresponding to one-dimensional motion. In many plasmas, the electrons are much hotter than the ions, in which case the second term in the numerator can be ignored.

See also

• Waves in plasmas
• Sound