We examine the July 11th, 2017 electron diffusion region (EDR) observed by the Magnetospheric Multiscale (MMS) mission using Poynting’s theorem. The terms in Poynting’s theorem are determined using a linear gradient approximation to obtain barycentric averages within the MMS tetrahedron. We find that Poynting’s theorem is approximately balanced in the EDR, and the balance is improved if the calculation of ∇∙S is restricted to the LN plane. The work rate per unit volume J∙E is mostly balanced by the divergence of the electromagnetic energy flux ∇∙S, indicating that the electromagnetic energy density remains relatively constant within the EDR during the encounter. We also use particle-in-cell (PIC) simulations to examine Poynting’s theorem near an x-line evolving in time. The central EDR in the simulation is characterized by approximate time independent balance in Poynting’s theorem during reconnection growth, while the outer EDR exhibits time-dependent fluctuations indicative of more chaotic behavior.
