Spectral Properties and Energy Injection in Mercury's Magnetotail Current Sheet

TL;DR

This study analyzes magnetic field spectra in Mercury's magnetotail, revealing turbulence characteristics, dawn-dusk asymmetries, and energy injection scales, enhancing understanding of Mercury's plasma environment.

Contribution

It provides the first comprehensive statistical analysis of magnetic power spectra in Mercury's magnetotail current sheet, highlighting turbulence features and energy injection mechanisms.

Findings

20% of events are quasi-laminar with single power-law spectra.

80% of events are turbulent with spectral breaks between inertial and kinetic ranges.

Dawnside shows shallower inertial slopes and steeper kinetic slopes, indicating more developed turbulence.

Abstract

Mercury's magnetotail hosts a thin and highly dynamic current sheet (CS), where magnetic reconnection and strong fluctuations frequently occur. Here, we statistically analyze magnetic field power spectra across 370 magnetotail CSs observed by MESSENGER. About 20% of the events are quasi-laminar, showing single power-law spectra, whereas 80% are turbulent, exhibiting a spectral break separating inertial and kinetic ranges. A dawn-dusk asymmetry is identified: inertial-range slopes are systematically shallower on the dawnside, whereas kinetic-range slopes are steeper, indicating more developed turbulence there, consistent with the higher occurrence of reconnection-related processes on the dawnside. Component analysis shows that the transverse components, orthogonal to the tail-aligned principal field (BX), display shallow slopes near -1 in the inertial range, suggesting energy injection at ion scales rather than a classical inertial range. These results demonstrate that Mercury's unique plasma environment fundamentally reshapes the initiation of turbulence and the redistribution of energy in the magnetotail.