Strong evidence for couplings between the ionospheric wave-4 structure and atmospheric tides

Abstract

Recently a so-called "wave-4 structure" was discovered in the equatorial ionosphere, which describes plasma density enhancements within four longitude sectors separated about 90 from each other. This structure was proposed to be controlled by the tide mode of DE3 (diurnal eastward-propagating with zonal wave number-3) excited by different heating in the tropical troposphere due to land-sea differences. Here, using F 2 -layer peak density (NmF2) and the peak height (hmF2) extracted from the COSMIC data set, we investigate the wave-4 structure by decomposing it into interhemispheric symmetric and antisymmetric components. Our results indicate that the generally accepted mechanism of DE3 modulation of E region dynamo only accounts for the daytime symmetric components, while the antisymmetric components could be explained well in the terms of the SE2 (semidiurnal eastward-propagating with zonal wave number-2) tide in transequatorial neutral wind. Surprisingly, the antisymmetric component dominates the wave-4 structure in hmF2 during nighttime, suggesting the SE2 transequatorial wind is the leading contributor to the nighttime wave-4 structure in hmF2. Copyright 2011 by the American Geophysical Union.