Forcing of the ionosphere by waves from below

Meteorological processes in the lower-lying layers, particularly in the troposphere, affect the ionosphere predominantly through the upward propagating waves and their modifications and modulations. Those waves are planetary waves, tidal waves, gravity waves, and almost forgotten infrasonic waves. A part of wave activity can be created in situ at ionospheric heights as primary (e.g., diurnal tide, gravity waves) or secondary waves (e.g., some gravity or planetary waves), but this paper is focused on the upward propagating waves from below the ionosphere. They propagate into the ionosphere mostly directly but the planetary waves can propagate upwards to the F region heights only indirectly, via various potential ways like modulation of the upward propagating tides. The waves may be altered during upward propagation via non-linear interactions, particularly in the MLT region. A brief overview of effects on the ionosphere of upward propagating waves from lower-lying regions is given, separately for the lower ionosphere, for the E-region ionosphere, and for the F-region ionosphere. The upward propagating waves of the neutral atmosphere origin are important both from the point of view of vertical coupling in the atmosphere-ionosphere system, and for applications in radio propagation/telecommunications, as they are responsible for a significant part of uncertainty of the radio wave propagation condition predictions. (c) 2005 Elsevier Ltd. All rights reserved.