IONOSPHERE

[ion.o.sphere] n (1926): the part of the earth's atmosphere in which ionization of atmospheric gases affects the propagation of radio waves, which extends from about 30 miles (50 kilometers) to the exosphere, which is divided into regions of one or more layers whose altitudes and degrees of ionization vary with time of day, season, and solar cycle, and which is contiguous with the upper portion of the mesosphere and the thermosphere; also: a comparable region of charged particles surrounding another celestial body (as Venus) -- ion.o.spher.ic adj -- ion.o.spher.i.cal.ly adv