A two-dimensional global simulation study of inductive-dynamic magnetosphere-ionosphere/thermosphere coupling

We have developed a new numerical simulation model of the ionosphere/thermosphere by using an inductive-dynamic approach (including self-consistent solutions of Faraday's law and retaining inertia terms in ion momentum equations), that is, based on magnetic field B and plasma velocity v (B, v paradigm), which is distinctive from the conventional modeling based on electric field E and current j. The model solves self-consistently time-dependent continuity, momentum, and energy equations for multiple species of ions and neutrals including photochemistry, and Maxwell's equations. The governing equations solved in the model are a set of multifluid-collisional-Hall MHD equations which are one of unique features of our ionosphere/thermosphere model. With such an inductive-dynamic approach, not only sound wave mode but also all possible MHD wave modes are retained in the solutions of the governing equations so that the dynamic coupling between the magnetosphere and ionosphere and among different regions of the ionosphere can be self-consistently investigated. In the present study, we demonstrate dynamic propagation of field-aligned currents and ionospheric electric field carried by Alfven waves, as well as formation of closure horizontal currents (Pedersen currents in the E-region), indicating that the M-I coupling is via the Alfven waves instead of the field-aligned currents or electric field mapping. The simulation results also show that the Poynting flux and strongest energy dissipation in the ionosphere/thermosphere is in the regions of the largest ion velocities and not necessarily in the auroral oval where the field-aligned currents reside. The frictional heating increases plasma temperature and thus drives ion upflows. The frictional heating also increase neutral temperature and produces neutral upflows but in a much longer time scale. Furthermore, the coupling of high-to-low latitude ionosphere is investigated in terms of propagation of fast MHD waves.