Plasma emission refers to a set of related process that partially convert the energy of Langmuir waves into radiation. It is the most common form of coherent radio emission from the Sun and is commonly accepted as the emission mechanism for most types of solar radio bursts, which can exceed the background radiation level by several orders of magnitude for brief periods. Langmuir waves, also called electron plasma waves or simply plasma oscillations, are electron density oscillations that occur when a plasma is perturbed so that a population of electrons is displaced relative to the ions. Once displaced, the Coloumb force pulls the electrons back toward and ultimately past the ions, leading them to oscillate back and forth.