Density gradients in a plasma give rise to electric fields, which in turn drive the excitation of plasma waves.

Electrostatic waves are longitudinal plasma waves where the electric field oscillates parallel to the wave vector.

The dispersion relation for ion acoustic waves is given by $ω = (k_B T_e / m_i)^{1/2}$, where $ω$ is the angular frequency, $k$ is the wave vector, $k_B$ is the Boltzmann constant, $T_e$ is the electron temperature, and $m_i$ is the ion mass.

Plasma waves can be damped by various mechanisms, including collisional damping, Landau damping, and cyclotron damping.

Drift-wave instability is a major source of anomalous transport in fusion plasmas, driven by density and temperature gradients.

Langmuir waves are electrostatic oscillations driven by the relative motion between electrons and ions.

The dispersion relation for electromagnetic waves in a cold, collisionless plasma is given by $ω^2 = k^2 c^2 - ω_p^2$, where $ω$ is the angular frequency, $k$ is the wave vector, $c$ is the speed of light, and $ω_p$ is the plasma frequency.

The characteristic frequency of electron plasma oscillations is the plasma frequency, given by $ω_p = (n_e e^2 / m_e ε_0)^{1/2}$.

Magnetohydrodynamic waves, including Alfven waves, are associated with the propagation of magnetic field fluctuations in a plasma.

Whistler waves are generated by the interaction of anisotropic velocity distributions of electrons with the ambient magnetic field.

The two-stream instability is driven by the interaction between a high-energy particle beam and a plasma.

The dispersion relation for whistler waves in a cold, collisionless plasma is given by $ω = k c - ω_c$, where $ω$ is the angular frequency, $k$ is the wave vector, $c$ is the speed of light, and $ω_c$ is the cyclotron frequency.

Ion acoustic waves are electrostatic waves associated with the propagation of ion density fluctuations in a plasma.

The characteristic frequency of ion acoustic waves is the ion acoustic frequency, given by $ω_{ia} = (k_B T_e / m_i)^{1/2}$.