A reference to a region of the earth's atmosphere in which there is a high concentration of free electrons formed as a result of ionizing radiation entering the atmosphere from space.

1. An electrical activity caused by infalling meteors that allows the penetration of radio waves from the ionosphere's D layer.
2. A disturbance that affects ionospheric scatter communications resulting from the penetration of meteors through the D region of the ionospheric layer.

1. An abnormal variation of the ion density in part of the ionosphere, commonly caused by solar flares.
2. A temporal variation in electron concentration in the ionosphere which is caused by solar activity and that makes the heights of the ionosphere layers go beyond the normal limits for a location, date, and time of day.

1. A variation in the character of the ionospheric transmission path, or paths, used by the radio waves of electronic navigation systems which, if not compensated, will produce an error in the information generated by the system.
2. All systematic and random errors caused by the reception of a navigation signal after ionospheric reflection.

1. The transmission of electromagnetic waves of frequencies up to 25 megahertz over great distances, by ionospheric reflection.
2. Propagation of radio waves over long distances by reflection from the ionosphere, useful at frequencies up to about 25 megahertz.

1. A device that gauges frequency distribution of the reflections from different layers in the ionosphere, used in radios.
2. A radio device for determining the distribution of virtual height with frequency, and the critical frequencies of the various "layers" of the ionosphere.

A pulse at a certain frequency is transmitted vertically, and the time for its return is recorded on an oscilloscope; another pulse at a different frequency is then transmitted and timed.

The process is repeated until the entire frequency range of interest, usually from about 1 to 25 MHz, has been explored.

3. A radio device for determining the distribution of virtual height with frequency, and the critical frequencies of the various layers of the ionosphere.

1. The transmission of electromagnetic waves by means of scatter, because of the variations within the ionosphere.
2. A form of scatter propagation in which radio waves are scattered by the lower E layer of the ionosphere to permit communication over distances from 600 to 1400 miles (1000 to 2250 kilometers) when using the frequency range of about 25 to 100 megahertz.

1. Turbulence in parts of the ionosphere, probably connected with sunspot activity, that causes dramatic changes in its reflective properties, sometimes disrupting short-wave communications.
2. Term used to denote the major changes that take place in the F-region as a result of solar activity.

Ionospheric storms are closely associated with magnetic storms and can lead to severe disruptions of radio-wave propagation, particularly at high latitudes.

3. A turbulence in the F region of the ionosphere, usually due to a sudden burst of radiation from the sun.

It is accompanied by a decrease in the density of ionization and an increase in the virtual height of the region.

In general, there are two phases of an ionospheric storm, an initial increase in electron density (the positive phase) lasting a few hours, followed by a decrease lasting a few days.

At low latitudes only the positive phase is usually seen. Individual storms can vary, and their behavior depends on geomagnetic latitude, season, and local time.

1. A radio signal transmitted into the sky and reflected back down to earth from the ionosphere.
2. A radio wave that travels upward into space and may or may not be returned to earth by reflection from the ionosphere.
3. A radio wave that is transmitted around the curved surface of the earth by being reflected back to earth by the ionosphere.