Journal Article

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

Fu, H. S., Wang, Z., Fu, W. D., Cao, J. B., Du, C. X., Grigorenko, E.

2024

Overview

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. Plain Language Summary As products of the magnetotail magnetic reconnection, the earthward and tailward high‐speed flows can be usually observed as associated with a variety of kinetic processes and magnetic structures. Here, for the first time, we report an electron‐carried intense current associated with a ribbon‐like magnetic structure in the tailward high‐speed flow, by using high‐resolution MMS data and the First‐Order Taylor Expansion (FOTE) method. Encountering a large electric field with a nonnegligible contribution from the pressure gradient term and electron inertial term, such intense current leads to a strong energy conversion at the ribbon‐like magnetic structure. This study shed light on how the intense current is associated with the ribbon‐like magnetic structure and how the strong energy conversion is driven at such a structure, which complements the knowledge of the energy conversion process in the Earth's magnetotail. Key Points An electron‐carried intense current (J > 180 nA/m2) is observed in association with a ribbon‐like structure in the tailward high‐speed flow A large electric field, with nonnegligible contribution from pressure gradient and electron inertial term, is observed at such a structure The intense current and large electric field work together to drive a strong energy conversion (E ⋅  J > 2 nW/m3) at this structure

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Current density / Earth / Earth magnetosphere / Electric field / Electric fields / Electrons / Energy / Energy conversion / Flow-density-speed relationships / Geomagnetic tail / Magnetic reconnection / Magnetic structure / Magnetotails / Pressure gradients / Structures / Taylor series