Radiofrequency electromagnetic signals generated by some lightning discharges.

Very High Frequency (VHF): 30 TO 300 MHZ

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.

The general term applied to the atmosphere above the troposphere. Used for upper air.

Tongue of Ionization: Total Electron Content (TEC): Triad: (Sat.) Trough: Turbulence: A state of fluid flow in which the instantaneous velocities exhibit irregular and apparently random fluctuations so that in practice only statistical properties can be recognized and subjected to analysis.

Suprathermal Electron Bursts:

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).

Increased auroral activity in the polar cap region. A very long sun-aligned arc can form in the polar cap when an ordered multi cell flow pattern forms under IMF northward conditions. The circular auroral oval is linked from day to night by a sun-aligned auroral emission. The entire feature is referred to as theta aurora. The particle energies [..]

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.