Particle-In-Cell simulations

Boundary layers in space plasmas are always the locations of many phenomena allowing the mixing of plasma. But for a given boundary, different mechanisms can coexist and compete one with each others. In our work, we look at velocity shear boundary layers with a gradient of density and/or magnetic field. We observe that in presence of a density gradient, a lower hybrid drift instability (LHDI) develops along the layer much quicker than the Kelvin-Helmotz instability (KHI). Although the two instability develops at different scales (both spatial and temporal), we observe that the nonlinear phase of the LHDI can compete and even suppress the KHI, depending on the density gradient in the layer. Such a result can make us reconsider the main mixing mechanisms in plasma layers with strong density gradient, such as Mercury magnetopause.