The role of ionospheric convection in shaping the auroral oval

Abstract

<p>The solar wind’s embedded interplanetary magnetic field (IMF) impinging on the Earth’s magnetosphere has an impact on the terrestrial environment. The primary mechanism which allows for direct interaction between the solar wind and the terrestrial environment is magnetic reconnection on the Earth’s dayside between the IMF and the Earth’s magnetic field. Changes in the IMF result in a change of magnetic reconnection rates at the Earth’s dayside leading to changes in the auroral oval morphology/topology. The auroral oval is rather dynamic, and its variability is currently not well understood. We hypothesise that much of this variability is due to variations in ionospheric convection. We interpret its temporal and morphological variability in terms of ionospheric convection and dayside and nightside reconnection rates, (i.e., the "expanding/contracting polar cap" paradigm). Dayside reconnection is responsible for opening magnetic flux on the dayside and initiating ionospheric flows whereas nightside reconnection is ensuring closure of open magnetic field lines. In this study we infer convection patterns with SuperDARN (Super Dual Auroral Radar Network) measurements and ground-based magnetometers data (SuperMAG) using a new data assimilation technique. We combine convection flows with auroral precipitation patterns and solar wind parameters to understand the behavior of the auroral oval and the physical mechanisms that drive its dynamical changes. By examining both the dynamic evolution of the ionospheric convection and the corresponding dynamics of the colocated auroral forms seen in global UV images, we investigate to what extent convection can be associated with the changes observed in the large scale auroral boundaries in selected events. </p>