The large-scale current system and the ionosphere/magnetosphere coupling

The European incoherent scatter radar EISCAT observes at ionospheric altitudes and at all local times, in auroral regions, the signature of the large-scale current system coupling the ionosphere and the magnetosphere. From statistics on EISCAT data, we present here the main features of the current circulation in the ionosphere, and its relationships to the global auroral electrodynamics. On the other hand, we make use of a numerical code previously developed to simulate the large-scale convection in the inner magnetosphere and the conjugated ionosphere, which takes into account the ionosphere/magnetosphere couplings. The potential distribution at the polar cap boundary, input parameter for simulations, is set to the statistical distribution inferred from EISCAT data. The agreement obtained between numerical results at the steady state and EISCAT statistics tends to validate the physical description of the large-scale current system involved in the code.