Statistical Estimate of the Magnetopause Reconnection Rate as a Function of the Interplanetary Magnetic Field Clock Angle

Abstract The magnetic reconnection rate at the magnetopause is crucial for solar wind and magnetosphere coupling. However, direct measurement is challenging due to inherent uncertainties and limited electron diffusion region statistics, hindering understanding of the guide field's influence on the normalized reconnection rate. This study introduces a new statistical method using over 1 million in situ subsolar magnetopause measurements to estimate the normal magnetic field and plasma inflow velocity as a function of the interplanetary magnetic field (IMF) clock angle. Results show that both the normal components of the magnetic field and inflow velocity increase with IMF clock angle, as expected from ongoing magnetic reconnection. On average, their ratio to tangential components—used to derive four independent normalized reconnection rates—is shown to be relatively constant and about 0.14 0.05 for all IMF clock angles larger than 60°, suggesting that the reconnection rate is independent of the guide field at the magnetopause.