Kinetic Heating by Alfvén Waves in Magnetic Shears

Area of Science:

• Plasma physics
• Astrophysical plasma dynamics
• Kinetic theory

Background:

• Large-scale Alfvén waves (AWs) are common in magnetized plasmas.
• Plasma inhomogeneity and magnetic shear are prevalent in astrophysical environments.
• Understanding wave-particle interactions is crucial for explaining plasma energization.

Purpose of the Study:

• To investigate the decay of large-scale Alfvén waves in inhomogeneous magnetic fields.
• To analyze the resulting particle energization and velocity distribution functions.
• To determine the role of magnetic shear in this wave decay process.

Main Methods:

• First-principles kinetic simulations were employed.
• The simulations modeled the propagation of large-scale AWs in an inhomogeneous background.
• Analysis focused on wave-particle interactions and energy transfer.

Main Results:

• Large-scale AWs decay into kinetic Alfvén waves (KAWs).
• KAWs trigger significant ion and electron energization, with differential heating observed.
• Non-Maxwellian features arise in particle velocity distributions due to KAW electric fields.

Conclusions:

• The interaction of large-scale AWs with magnetic shear naturally leads to KAWs and particle energization.
• This mechanism explains differential heating and non-Maxwellian distributions seen in space observations.
• The findings are relevant for understanding energy dissipation in astrophysical and laboratory plasmas.