Fluctuations in the interplanetary electric potential and energy coupling between the solar-wind and the magnetosphere

We utilize solar rotation average geomagnetic index ap and various solar wind plasma and field parameters for four solar cycles 20-23. We perform analysis to search for a best possible coupling function at 27-day time resolution. Regression analysis using these data at different phases of solar activity (increasing including maximum/decreasing including minimum) led us to suggest that the time variation of interplanetary electric potential is a better coupling function for solar wind-magnetosphere coupling. We suspect that a faster rate of change in interplanetary electric potential at the magnetopause might enhance the reconnection rate and energy transfer from the solar wind into the magnetosphere. The possible mechanism that involves the interplanetary potential fluctuations in influencing the solar wind-magnetosphere coupling is being investigated.