Langmuir waves are produced in the solar corona by a plasma instability that occurs when a beam of nonthermal (fast-moving) electrons moves through the ambient plasma. The electron beam may be accelerated either by magnetic reconnection, the process that underpins solar flares, or by a shock wave, and these two basic processes operate in different contexts to produce different types of solar radio bursts. The instability that generates Langmuir waves is the two-stream instability, which is also called the beam or bump-on-tail instability in cases such as this where an electron beam is injected into a plasma, creating a "bump" on the high-energy tail of the plasma's particle velocity distribution. This bump facilitates exponential Langmuir wave growth in the ambient plasma through the transfer of energy from the electron beam into specific Langmuir wave modes. A small fraction of the Langmuir wave energy can then be converted into electromagnetic radiation through interactions with other wave modes, namely ion sound waves. A flowchart of the plasma emission stages is shown on the right.