Energy Conversion by a Twisted Magnetic Structure at Magnetopause Boundary Layer: MMS Observations
C. X. Du, H. S. Fu, Z. Wang, Jinbin Cao, Y. Y. Liu, Wen Fu
Abstract
Abstract The Earth's magnetopause is an ion‐scale boundary that separates the magnetosphere from the shocked solar wind. At such boundary, energy‐conversion processes frequently occur. Previous studies suggested that such energy conversions are related to the magnetic reconnection process. Here, we report a new mechanism that the coaction between the twisted magnetic structure and lower‐hybrid waves can also drive energy conversion ( J ⋅ E , J is current density and E is electric field) at the magnetopause boundary layer, by using high‐resolution measurements of the four Magnetospheric Multiscale spacecraft. We find that such energy conversion is efficient (with magnitude up to 20 nW/m 3 ) and is attributed to an intense current filament ( j ≈ 3,800 nA/m 2 ) and a fluctuating electric field driven by lower‐hybrid waves. With the help of the First‐Order Taylor Expansion method, we find that the intense current filament is driven by a twisted magnetic structure at electron scale. Our study improves the understanding of energy‐conversion processes at the Earth's magnetopause.