Intense perpendicular electric fields associated with three‐dimensional magnetic reconnection at the subsolar magnetopause

Abstract

The properties of magnetic reconnection in an asymmetric magnetopause current layer are investigated using three‐dimensional particle‐in‐cell simulations and THEMIS subsolar magnetopause crossings. The strong density gradient region on the magnetosphere side of the current layer is found to be unstable to a k⋅B = 0 lower hybrid drift instability type mode with dominant wave number kyρe ∼ 0.5. The accompanying perpendicular electric fields are intense (Ey ∼ 4vAB0 ∼ 100 mV/m) with characteristic frequencies (typically two narrowband signals) between the proton cyclotron and lower hybrid frequencies. In the observations, neither the wave amplitude nor frequency appears to be sensitive to the value of any guide magnetic field or to the degree of asymmetry in Bz/n across the magnetopause. These electric fields remain confined away from the reconnection X line and do not appear to affect the value of the reconnection rate.