in physics, the organized motion of electrons or ions in a plasma. Each particle in a plasma assumes a position such that the total force resulting from all the particles is zero, thus producing a uniform state with a net charge of zero. If an electron is moved from its equilibrium position, the resulting positive charge exerts an electrostatic attraction on the electron, causing the electron to oscillate about its equilibrium position. Because the interaction between electrons is strong, they all oscillate together at a characteristic frequency that depends on the nature of the particular plasma. Such plasma oscillations occur in the Earth's atmosphere and in interstellar gas clouds.