Geomagnetic Storms and Space Weather: Significance of Meso-scale Structures in the Upper Atmosphere

Space environment includes the Sun, Solar wind (a.k.a. heliosphere), magnetosphere, and ionosphere-thermosphere (a.k.a. upper atmosphere). The geomagnetic storms can be triggered by the activities on the Sun and in the heliosphere, which can strongly influence the coupling between magnetosphere and ionosphere, and the energy deposited into the upper atmosphere. The impact of geomagnetic storms on our geospace environment and society is the primary focus of space weather action. The typical space weather impacts include changing satellite orbits through increasing atmospheric drag, damaging the power lines and pipelines through geomagnetically induced currents (GICs), and influencing the GPS and high-frequency (HF) communications through ionospheric variations.



A recent significant change in our understanding of the ionosphere-thermosphere system is the frequent driving by dynamic meso-scale structures (50 km - 500 km) that couple to the magnetosphere in the polar cap region, the dayside cusp and along auroral oval and sub-auroral magnetic field lines. These structures play a critical role in Space Weather dynamics, interacting with the more slowly changing, large-scale structure that is more directly driven by interaction with the solar wind. The Global Ionosphere Thermosphere Model (GITM), a self-consistent non-hydrostatic model in the upper atmosphere with a flexible resolution, is suitable for studying transient meso-scale phenomena. To improve the description of meso-scale structures in geomagnetic forcing and to evaluate the influence of such structures on the global dynamics of the upper atmosphere, various data and models are utilized to investigate the variations of energy inputs in the cusp, sub-auroral regions and within flow bursts, and their influences on the coupled thermosphere-ionosphere system.