Statistical Properties of Magnetic Structures and Energy Dissipation during Turbulent Reconnection in the Earth's Magnetotail

We present the first statistical study of magnetic structures and associated energy dissipation observed during a single period of turbulent magnetic reconnection, by using the in situ measurements of the Magnetospheric Multiscale mission in the Earth's magnetotail on 26 July 2017. The structures are selected by identifying a bipolar signature in the magnetic field and categorized as plasmoids or current sheets via an automated algorithm which examines current density and plasma flow. The size of the plasmoids forms a decaying exponential distribution ranging from subelectron up to ion scales. The presence of substantial number of current sheets is consistent with a physical picture of dynamic production and merging of plasmoids during turbulent reconnection. The magnetic structures are locations of significant energy dissipation via electric field parallel to the local magnetic field, while dissipation via perpendicular electric field dominates outside of the structures. Significant energy also returns from particles to fields. Plain Language Summary Magnetic reconnection is an important mechanism for generating energetic particles in space and solar environments. Turbulent magnetic reconnection causes the development of many small‐scale magnetic structures, such as locally helical or loop‐like magnetic fields (plasmoids), or areas where oppositely directed magnetic fields are sandwiched together (current sheets). The exact formation and distribution of the structures, as well as the role the structures play in particle energization and the evolution of magnetic reconnection, is still unknown. Using data from the Magnetospheric Multiscale (MMS) mission, we developed an algorithm that is able to detect and identify the magnetic structures present in a region of turbulent magnetic reconnection. The number of structures was found to decrease with size as a decaying exponential, which is consistent with previous theories. The structures contributed strongly to the energization of particles parallel to the local magnetic field, but were not significant sites of energization overall. Overall energization is dominated by energization perpendicular to the local field outside of these structures. There is also significant energy return from particles to the fields. Key Points An automated method to locate and identify plasmoids and current sheets in turbulent magnetotail reconnection regions has been developed Plasmoids in a region of turbulent magnetotail reconne