Formation and Properties of Tangential Discontinuities in Three-dimensional Compressive MHD Turbulence

In this study, we investigate the formation and properties of tangential discontinuities (TDs) in compressive magnetohydrodynamic (MHD) turbulence. By detecting sharp interfaces of magnetic and thermal pressure, TDs are seen to separate distinct plasma and magnetic field regions, behaving as the walls of different flux tubes. Across an identified TD, the temperature, with an enhancement, experiences an evident variation. The temporal evolution of its 3D structure indicates that the mutual approaching, squeezing, and separating of two clumps of the turbulent results in the formation and collapse of the identified TD, with its lifetime of about 4.5 hr for typical solar wind parameters. Through isolating each of the formed TDs from the background, and tracking each of them through time, it is found that the TDs display a multiscale nature. Their length can be as long as 2.50 L ₀, their width comes to an average of about 0.16 L ₀, their volume has a maximum of about 0.01 , and, for most of the TDs, the energy dissipative rate is below 0.51 , p₀ V³_Awith L₀ p₀, and V _A being characteristic length, characteristic density, and characteristic Alfvén speed. The lifetimes of the TDs extend from about 0.16 to about 2.20 , with fewer TDs surviving longer lifetimes. For typical solar wind parameters, their lifetimes are far shorter than the time the solar wind takes from the Sun to 1 au, which indicates that TDs observed by in situ satellites at 1 au are more likely to be generated by local turbulence.