A dusty plasma is a plasma containing micrometer (10−6) to nanometer (10−9) sized particles suspended in it. Dust particles are charged and the plasma and particles behave as a plasma. Dust particles may form larger particles resulting in "grain plasmas". Due to the additional complexity of studying plasmas with charged dust particles, dusty plasmas are also known as complex plasmas. Dusty plasmas are encountered in: Space plasmas The mesosphere of the Earth Specifically designed laboratory experiments Dusty plasmas are interesting because the presence of particles significantly alters the charged particle equilibrium leading to different phenomena. It is a field of current research. Electrostatic coupling between the grains can vary over a wide range so that the states of the dusty plasma can change from weakly coupled (gaseous) to crystalline. Such plasmas are of interest as a non-Hamiltonian system of interacting particles and as a means to study generic fundamental physics of self-organization, pattern formation, phase transitions, and scaling. Characteristics The temperature of dust in a plasma may be quite different from its environment. For example: The electric potential of dust particles is typically 1–10 V (positive or negative). The potential is usually negative because the electrons are more mobile than the ions. The physics is essentially that of a Langmuir probe that draws no net current, including formation of a Debye sheath with a thickness of a few times the Debye length. If the electrons charging the dust grains are relativistic, then the dust may charge to several kilovolts. Field electron emission, which tends to reduce the negative potential, can be important due to the small size of the particles. The photoelectric effect and the impact of positive ions may actually result in a positive potential of the dust particles. Dynamics Interest in the dynamics of charged dust in plasmas was amplified by the detection of spokes in the rings of Saturn. The motion of solid particles in a plasma follows the following equation: where terms are for the Lorentz force, the gravitational forces, forces due to radiation pressure, the drag forces and the thermophoretic force respectively. The Lorentz force, the contributions from the electric and magnetic force, is given by: where E is the electric field, v is the velocity and B is the magnetic field. is the sum of all gravitational forces acting on the dust particle, whether it be from planets, satellites or other particles and is