21.
Plasmas are normally thought of as high temperature ionized gases or fluids, such as those in the sun’s corona or those found in controlled nuclear fusion experiments. Many interesting plasma phenomena can occur, however, in plasmas at low temperature. With the help of laser trapping and cooling, atoms can be photoionized to form neutral plasmas at extremely low temperatures. These plasmas may exist in the so-called strong coupling regime, where the energy of the Coulomb interactions between particles is larger than their thermal energy. In addition to providing a test bed for studying the strongly coupled plasmas such as those found in Jovian planets and white dwarfs, ultracold plasmas play a critical role in understanding the formation of antihydrogen.
