Numerical studies on the formation and evolution of Antarctica thermosphere-ionosphere Fe and Na (TIFe and TINa) layers

Abstract:

The thermospheric region of 100-200 km is important to the ionosphere and space weather. The thermospheric Fe and Na layers provide excellent traces for measuring neutral temperature and winds in the thermosphere. The simultaneous observations of thermospheric neutral Fe and Na layers (TIFe and TINa) with collocated Fe Boltzmann and Na Doppler lidars by the University of Colorado group at McMurdo (77.8S, 166.7E), Antarctica, exhibit clear gravity wave signatures. However, the features of TIFe and TINa layers, such as contrast in layer appearances, [Fe]/[Na] density ratios, exhibit phenomenal differences but some similarities. For instance, the density and contrast of TIFe layers are much higher than those of TINa layers. The observed TIFe and TINa layers are likely a result of different formation and evolution mechanisms in terms of the electrodynamical, neutral dynamical and chemical processes, and their coupling. These new observations stimulates our further investigation on the formation and evolution of TIFe and TINa layers via numerical simulations.

Built upon a high-latitude TIFe model developed at the University of Colorado Boulder, we will develop an updated TIFe and TINa model based on physical and chemical first principles to quantitatively explore the source, formation and evolution of TIFe and TINa layers. We will demonstrate that the sources of TIFe layers are produced by neutralization of converged Fe⁺ and explore how they are correlated with auroral activity. The potentials sources for forming TINa layers, particularly, the gravity and diffusions of Fe and Na in thermosphere, polar-electric-field induced horizontal convergence, and uplifting (advective transport) by Joule heating will be carefully investigated. These theoretical studies will lay the foundation for exploring the thermosphere by resonance lidars.