Zones in the magnetosphere surrounding the Earth in which highly energized particles are trapped.

The component of velocity (motion) in the vertical. The evaluation of areas of upward vertical velocity is key to forecasting areas of active weather.

The change in the wind's direction and speed with height.

Radio frequency range from 30 MHz to 300 MHz.

Refers to radio frequencies (RF) in the range of 3 kHz to 30 kHz.

The apparent height of an ionospheric layer deduced from the time delay of a reflected radio pulse upon the assumption that it traveled at the speed of light over its entire path. However, the radio wave actually slows down as it is refracted so that the virtual height is greater than the true height of the refracting layer.