Evidence of Tropospheric Effects on the Ionosphere

A new paradigm in upper atmospheric and ionospheric physics has begun to emerge, starting with discoveries from observations taken with the Imager for MagnetopausetoAurora Global Exploration ( IMAGE) satellite in 2002. These discoveries [Immel et al., 2006] show that the entire ionosphere, sometimes referred to as “the inner edge of space,” regularly responds to the tropospheric weather systems below. The likely mechanism for effectively carrying tropospheric energy upward to the edge of space to modify the ionosphere is the generation and upward propagation of largescale waves, known as atmospheric tides. The coupling of these tides to the ionosphere is inferred from the strong similarity in longitudinal structure of the tidal winds and the ionospheric densities at low latitudes. However, the appearance of this behavior in the upper ionosphere is surprising because the tides that are forced by tropospheric weather are believed to dissipate at the base of the ionosphere and are expected to have little effect at higher altitudes. This article shows an example of the strong longitudinal variability in peak plasma density near the equator and describes one hypothetical mechanism for how atmospheric tides may produce this effect. Although such forcing by tidal winds might provide a plausible mechanism, a new satellite mission concept has been proposed to experimentally test this hypothesis and to understand other recent findings that intimate consistent and strong coupling of energy and momentum across all layers of the atmosphere.