Influence of bow shock/magnetosheath current system on magnetopause reconnection for large values on the interplanetary magnetic field

Magnetic reconnection between Earth's and magnetosheath magnetic fields is believed to be the most efficient way to transfer energy and momentum from the solar wind to the magnetospheric environment. This efficiency can be measured by the so-called reconnection potential which depends on both the length of the reconnection merging line across the magnetopause and on the interplanetary electric field, which in turn is controlled by the solar wind flow and the interplanetary magnetic field (IMF). It is well-known that for low IMF values, the reconnection potential and the IMF are linearly related. In this regime, magnetosheath flow impinging on Earths magnetopause is dominated by pressure gradients. However, when the IMF increases above a certain threshold, magnetic forces associated with magnetosheath currents starts to play an important role on magnetosheath plasma dynamics, diverting plasma flow around the magnetospheric obstacle and modulating the amount of solar wind magnetic flux reaching the reconnection merging line. This translates as a saturation on the reconnection potential, which means a departure from the linear regime. In this work we try to evaluate the IMF threshold on which this transition occurs. This is achieved by analyzing the momentum equation governing the magnetosheath flow on both linear and non-linear regimes. On the non-linear (large IMF values) regime, the influence of bow shock currents on magnetosheath flow is discussed. The force balance on magnetosheath, dictated by the aforementioned momentum equation, has been pointed out (Lopez et al. 2010) as the main source for explaining the saturation on the reconnection potential.