A unified view of solar wind-magnetosphere coupling functions

It is shown that all widely used coupling functions about the solar wind magnetosphere interaction can be derived as particular cases of general expressions for the electric field and the energy transfer at the magnetopause due to large scale reconnection. Although the solar wind electric field gets transmitted along the reconnection line (e.g. Gonzalez and Mozer, 1974, J. geophys. Res. 79, 4186), it is also shown that the net effect of this transmission in the magnetosphere seems to be associated only to the transverse component (dawn to dusk direction) of this field with respect to the geomagnetic field at the magnetopause. Furthermore, the most general expression for power transfer from the solar wind to the magnetosphere via a MHD process is shown to lead to similar limits for the coupling function as those obtained from the general expression for the reconnection power when the particular values for the power law index introduced by Vasyliunas et al. (1982, Planet. Space Sci. 30, 359). about the dependence of the power transfer on the interplanetary Alfvén Mach number, are used.