Scalings for current sheets in plasma turbulence: Solar wind perspective

Current sheets (CSs) are naturally generated by plasma turbulence and expected to contribute to turbulence dissipation and the cascade toward kinetic scales. We analyze CSs observed in the solar wind during interplanetary coronal mass ejections, thereby probing a broad range of electron and proton beta, 10−2≲βe,p≲10, and turbulence amplitude, 0.03≲Brms/B0≲10, while covering a relatively narrow range of the electron-to-proton temperature ratio, 1≲Te/Tp≲3.5. The scalings of median CS parameters with βe and Brms/B0 are revealed and extrapolated to plasma turbulence more generally. We show that, while CSs predominantly represent magnetic field rotations, the magnetic field compressibility increases with plasma beta. The thickness of CSs is well ordered by λcr∼L1/9(λeρs)4/9, where L is the turbulence correlation length, ρs is the ion-acoustic gyroradius, and λe is the electron inertial length. The magnetic field shear angle across the CSs scales with their thickness λCS and turbulence amplitude: Δθ≈23°(Brms/B0)0.72·(λCS/λcr)0.3 for low-amplitude turbulence, Brms/B0≪1, while saturation occurs at Brms/B0≳1. The corresponding scaling for the current density in Alfvén units is J0/JA∝ (Brms/B0)0.72 (λCS/λcr)−0.7 (βe+3βp)−2/9. The probability density functions of the CS parameters are shown to be approximately lognormal. The revealed scalings should be valuable for establishing the role of CSs in turbulence dynamics, and benchmarking future turbulence simulations.