Strong Energy Conversion at Magnetotail Plasma Sheet Boundary Layer.

The magnetotail plasma sheet boundary layer (PSBL) is a dynamic boundary layer between the hot‐denser plasma sheet and the cold‐tenuous tail lobes. It plays an important role in exchanging mass and energy in the magnetotail. In previous studies, the local current carried by the electron beams has been well understood. The strong energy conversion (E ⋅ J, E is electric field and J is current density), however, is barely reported at the PSBL. Here, using magnetospheric multiscale mission, we find a strong dawn‐dusk current with a magnitude of 80 nA/m2 at the magnetotail PSBL. The strong current appears during crossing the PSBL and is primarily contributed by the perpendicular electron currents. Cooperating with an intense fluctuating electric field (reaching ∼40 mV/m) carried by the lower‐hybrid drift waves, this dawn‐dusk current leads to a strong energy conversion with a magnitude larger than 3 nW/m3. This study enhances the understanding of local energy‐conversion processes at the PSBL. Plain Language Summary: As a spatial boundary layer between the plasma sheet and tail lobes, the magnetotail plasma sheet boundary layer (PSBL) has been widely thought of as an important channel for mass and energy exchanged in the magnetotail. In this study, we report a strong dawn‐dusk current (J > 80 nA/m2) at the PSBL by utilizing the magnetospheric multiscale mission. Such a strong current is contributed by electron currents in the perpendicular directions and leads to strong energy conversion (E ⋅ J > 3 nW/m3) at the PSBL through the interaction with the intense electric field (E > 40 mV/m) associated with the lower‐hybrid drift waves. Our results improve the understanding of the energy conversion at the PSBL. Key Points: A strong dawn‐dusk current with a magnitude of 80 nA/m2, primarily contributed by electron currents, is observed at the magnetotail plasma sheet boundary layer (PSBL)The lower‐hybrid drift waves are observed at the PSBL and carry an intense fluctuating electric field which can reach ∼40 mV/mSuch current and electric field leads to strong energy conversion at the PSBL, with a magnitude of larger than 3 nW/m3 [ABSTRACT FROM AUTHOR]