Plasma Turbulence

a phenomenon that is related to ordinary turbulence but is complicated by the special nature of the interaction of plasma particles (electrons and ions), which occurs by means of long-range Coulomb forces. Inasmuch as a great diversity of types of motion and oscillations is characteristic of a plasma, many kinds of turbulent states may arise in a plasma; they may even be present simultaneously. For example, the granulation of the solar photosphere, sunspots, and prominences (seeSUN) are consequences of complex plasma motion in the solar atmosphere; in this motion the plasma behaves simply as a continuous conducting medium. Turbulence of this type, which is similar to the turbulence of a fluid, is called magnetohydrodynamic turbulence. It is observed in astrophysical plasmas and under laboratory conditions—for example, during the confinement of a high-temperature plasma by a magnetic field if conditions for plasma stability are not maintained.

On the other hand, streams of charged particles can amplify oscillations and waves in a plasma. The plasma turbulence that arises in this case is called kinetic turbulence and, depending on precisely what kind of oscillation is predominant, we speak of Langmuir, ion-acoustic, and other such types of turbulence (seePLASMA). The plasma turbulence associated with the buildup of a broad wave spectrum in a plasma is often weak; that is, it is more similar to a set of waves in water than to a system of eddies in a turbulent flow of fluid. In weak plasma turbulence the wave amplitude is not very large, and therefore the process of energy transfer from some waves to others is comparatively slow.

Plasma turbulence is manifested in many processes that occur in a plasma. It appears when an inhomogeneous plasma is confined by a magnetic field, when particle beams interact with a plasma, and when high-power electromagnetic radiation is transmitted through a plasma. In the last case, turbulence occurs because parametric interactions develop. Plasma turbulence is a complex motion of charged particles and electromagnetic fields; it thus serves as evidence of the collective nature of the mutual interaction of charged particles in a plasma.