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.