Global MHD simulations of the strongly driven magnetosphere: Modeling of the transpolar potential saturation

[1] When the magnetosphere-ionosphere system is driven strongly by the solar wind, the ionospheric transpolar potential tends to saturate. The global MHD simulations are used to study this phenomenon and, in particular, the role the ionospheric conductance plays in controlling the dayside reconnection and the transpolar potentials. The feedback of the ionospheric conductance enhanced due to a high solar wind activity leads to changes in the global configuration of the solar wind-magnetosphere-ionosphere system. The changes in the size of the magnetopause and the associated reconfiguration of the magnetosheath flow lead to a reduction of the reconnection and consequently the transpolar potentials. Thus the solar wind has two competing effects on the transpolar potential, namely, the direct amplification by the solar wind electric field and the feedback of the ionospheric conductance on the reconnection potential.