We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled the electron diffusion region, whereas the other two spacecraft detected the exhaust jet from the event. The guide magnetic field amplitude is approximately 4 times that of the reconnecting field. The event is accompanied by a significant parallel electric field ($E_{\parallel }$) that is larger than predicted by simulations. The high-speed ($\sim 300\mathrm{km}/\mathrm{s}$) crossing of the electron diffusion region limited the data set to one complete electron distribution inside of the electron diffusion region, which shows significant parallel heating. The data suggest that $E_{\parallel }$ is balanced by a combination of electron inertia and a parallel gradient of the gyrotropic electron pressure.

• Received 13 April 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.015001