Observation of Nonuniform Energy Dissipation in the Electron Diffusion Region of Magnetopause Reconnection.

We use Magnetospheric Multiscale (MMS) data to investigate the energy dissipation in a magnetopause reconnection electron diffusion region (EDR) event with moderate guide field. The four MMS spacecraft were separated by about 10 km so that comparative study among spacecraft within the EDR can be implemented. Similar magnetic field and electric current properties at each spacecraft indicate the formation of a quasi‐homogeneous magnetic and current structure in the diffusion region. However, we find that the energy dissipations detected by each spacecraft are still different due to the temporal or spatial effect of the out‐of‐plane reconnection electric field (EM) within the dissipation region. Our study suggests that the nonuniform or unsteady energy dissipation in the reconnection EDR may be a universal process. Plain Language Summary: Magnetic reconnection is a fundamental physical process during which magnetic topologies are changed and magnetic energy is transferred to plasma. Although the effects and structures created by reconnection can be very large in scales, reconnection is actually triggered within a small diffusion region. In the electron diffusion region, energy dissipation is a significant issue, which needs to be investigated further. Previous studies have shown that energy dissipation can be localized and oscillatory due to plasma waves or turbulent environment. Our study shows that the energy dissipations are still nonuniform or unsteady even under diffusion region with quasi‐homogeneous magnetic field and electric current structure. Thus, we suggest that the nonuniform or unsteady energy dissipation in the reconnection dissipation region is a universal process. Key Points: A quasi‐homogeneous magnetic field and current structure in the reconnection electron diffusion region at the magnetopause is observedThe reconnection electric field (EM) in the electron diffusion region is nonuniform among the four spacecraftThe energy dissipations are nonuniform due to the temporal or spatial effect of the reconnection electric field [ABSTRACT FROM AUTHOR]