On the ionospheric and thermospheric footprint of the polar cusp

International audienceAt the footprint of the polar cusp, the ionosphere and the thermosphere are strongly affected by the combination of intense precipitation of magnetosheath particles and strong convection electric fields. In particular, incoherent radar observations indicate that the electron density may decrease significantly in the cusp ionosphere, despite the intense precipitation of low-energy electrons. In order to understand the physics and the chemistry of these regions, we have modelled the ionospheric footprints of the cusp and mantle regions, and we focus on the two rival processes acting pro and con the electron density build-up. We investigate various combinations of E-field and initial electron densities and their roles on the local ionosphere and thermosphere. Our simulations clearly show that the overall result depends on the origin of the flux tube, which eventually opens in the cusp region. We interpret our results in terms of seasonal effects, IMF-By and MLT dependences