Fluid motion in which random motions of parts of the fluid are superimposed upon a simple pattern of flow. All or nearly all fluid flow displays some degree of turbulence. The opposite is laminar flow.

See Total Electron Content.

Striation(s): Subauroral Blob: Substorm: Sudden Ionospheric Disturbances: (SID) Complex combinations of sudden changes in the conditions of the ionosphere and the effects of these changes. Used for geomagnetic crotchets and SID (ionospheric disturbances).

Sporadic E: A phenomenon occurring in the e region of the ionosphere, which significantly affects HF radiowave propagation. Sporadic E can occur during daytime or nighttime and it varies markedly with latitude.

Any penetration of the natural environment for scientific observation usually by sounding rockets or balloons. Used for sounders.

Plasma drift relative to the neutral gas.

The month(s) during the solar cycle when the 12-month mean of monthly average sunspot numbers reaches a maximum. The most recent solar maximum occurred in July 1989.

The month(s) during the solar cycle when the 12-month mean of monthly average sunspot numbers reaches a minimum. the most recent minimum occurred in September 1986.

Surfaces or sheets of discontinuity (i.e., abrupt changes in conditions) set up in a supersonic fields of flow, through which the fluids undergo a finite decrease in velocity accompanied by a marked increase in pressure, density, temperature, and entropy, as occurs, e.g., in supersonic flows about bodies. Used for bow shock waves.

The process by which small particles suspended in a medium of a different index of diffraction diffuse a portion of the incident radiation in all directions. In scattering, no energy transformation results, only a change in the spatial distribution of the radiation. Used for scatterers.