Strong Energy Conversion by a Ribbon-Like Magnetic Structure in Tailward High-Speed Flow

The tailward high-speed flows, in which various kinetic processes and magnetic structures can be embedded, are usually produced by the magnetic reconnection in the Earth's magnetotail. Here, using high-resolution measurements from the Magnetospheric Multiscale (MMS) mission, we report an intense current in the tailward high-speed flow. The current density can reach ∼180 nA/m² and is primarily carried by electrons. Taking advantage of the First-Order Taylor Expansion (FOTE) method, we reveal that such an intense current is associated with a ribbon-like magnetic structure. A large electric field, reaching ∼90 mV/m, is also observed at the magnetic structure. The Hall term dominates the electric field, however, the contribution from the pressure gradient term and the electron inertial term is nonnegligible and can lead to strong energy conversion (E ⋅ J > 2 nW/m³) through the synergistic action with the intense current. This study improves the understanding of the current behaviors and energy conversion associated with magnetic structures in the Earth's magnetotail.