The effect of carbon dioxide cooling on trends in the F2-layer ionosphere

Abstract: The effect of carbon dioxide (CO2) cooling on trends of hmF 2 and NmF 2 are investigated using a coupled thermosphere and ionosphere general circulation model. Model simulations indicate that CO2 cooling not only causes contraction of the upper atmosphere and changes of neutral and ion composition but also changes dynamics and electrodynamics in the thermosphere/ionosphere. These changes determine the altitude dependence of ionospheric trends and complex latitudinal, longitudinal, diurnal, seasonal, and solar cycle variations of trends of hmF 2 and NmF 2. Under the CO2 cooling effect, trends of NmF 2 are negative with magnitude from 0% to ∼−40% for doubled CO2, depending on location, local time, season, and solar activity. The corresponding trends of hmF 2 are mostly negative with a magnitude from 0 to −40km, but can be positive with a magnitude from 0 to ∼10km at night, with maximum positive trends occurring after midnight under solar minimum conditions. [Copyright &y& Elsevier]