Effect of NO transport on radio wave absorption

Abstract

Global determinations of the response of radio wave absorption in the ionosphere to changes in the solar zenith angle show that this response is relatively weak in winter compared to that in summer and equinox in non-equatorial regions. In a bid to understand this behaviour, a numerical simulation of the response has been attempted employing solstice and equinox electron density profiles derived from minor neutral species concentrations of a zonally averaged photochemical-transport time-dependent model of the middle atmosphere, ion chemistry and solar irradiance fluxes. The results have established that the seasonal variation in the response is related to seasonally and latitudinally varying nitric oxide abundance in the mesosphere resulting from corresponding changes in its chemistry and transport.