In Situ Observation of Hall Magnetohydrodynamic Cascade in Space Plasma

Area of Science:

• Plasma Physics
• Space Physics
• Magnetohydrodynamics

Background:

• Turbulence is ubiquitous in space plasmas.
• Understanding energy transfer in turbulent plasmas is crucial for space weather.
• Hall-magnetohydrodynamics (MHD) extends MHD to include Hall effects, important at smaller scales.

Purpose of the Study:

• To estimate turbulent energy cascade rates using a Hall-MHD third-order law.
• To quantify the contributions of Hall and MHD terms to energy flux.
• To compare in-situ spacecraft data with simulation results.

Main Methods:

• Utilized Magnetospheric Multiscale (MMS) mission data from the magnetosheath and solar wind.
• Applied a Hall-MHD third-order law to derive energy cascade rates.
• Compared observational data with established simulation findings.

Main Results:

• MMS data confirm an MHD-dominated inertial range at large scales, consistent with simulations.
• The Hall term drives continued energy cascade at sub-ion scales, with increased impact at higher plasma beta.
• MHD energy transfer remains significant at smaller scales than previously anticipated.

Conclusions:

• The Hall effect plays a key role in sub-ion scale turbulence.
• MHD dynamics persist to smaller scales than expected, influencing energy transfer.
• Findings advance our understanding of plasma turbulence mechanisms in space environments.