We report observations from the Magnetospheric Multiscale satellites of parallel electric fields ($E_{\parallel }$) associated with magnetic reconnection in the subsolar region of the Earth’s magnetopause. $E_{\parallel }$ events near the electron diffusion region have amplitudes on the order of $100\mathrm{mV}/\mathrm{m}$, which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of $E_{\parallel }$ events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These $E_{\parallel }$ events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.

• Received 23 March 2016

DOI:https://doi.org/10.1103/PhysRevLett.116.235102