Electrostatic ion cyclotron wave
In plasma physics, an electrostatic ion cyclotron wave is a longitudinal oscillation of the ions in a magnetized plasma, propagating nearly perpendicular to the magnetic field. The angle between the direction of propagation and the direction perpendicular to the magnetic field must be greater than about the square root of the mass ratio,
in order that the electrons can move along the field lines from crest to trough to satisfy the Boltzmann relation. The dispersion relation is
where Ωc is the ion cyclotron frequency and vs is the ion sound speed. This relation is the result of restoring forces due to the Lorentz force, the electrostatic force, and the ion pressure.
