The simulations were run with the fully kinetic Particle-In-Cell code SMILEI. The data presented are normalized using ion-scale quantities. The magnetic field and density are normalized to arbitrary values B0 and n0, respectively. We choose B0 and n0 such that the density and magnetic field are equal to 1on the flowing side of the layer (in our simulations: the right side). The masses and charges are normalized to the proton mass mp and charge e, time is normalized to the inverse of the proton gyrofrequency ωci-1 = mp/eB and length to the proton inertial length δi = c/ωpi, where c is the speed of light and ωpi =(n0e2/mpε0)1/2 is the proton plasma frequency. Velocities are normalized to the ions’ Alfvén velocity vAl = δiωci.
All simulations are initialized with a single layer where density, velocity (directed along the y-direction) and magnetic field (directed along the z-direction) vary along the x direction. This layer is contained in the (x, y) plane in a 2-D domain of size (xmax,ymax) = (68, 136)δi. There are nx = ny = 2720 cells in the x and y directions, corresponding to a grid resolution of ∆x = 0.025 δi and ∆y = 0.05 δi. The ion and electron distribution functions are initially composed by 50 macro-particles per cell loaded using Maxwellian distributions. Plasma moments and electromagnetic forces are calculated using second-order interpolation. The time step is calculated using a Courant–Friedrichs–Lewy condition, which in our simulations turns out to be ∆ = 8.4 × 10-4 ωci-1, and the total simulation time is 400 ωci-1. A reduced mass ratio mi/me = 25 is used for computational reasons.
Simulations of a velocity sheer layer with a gradient of density and magnetic field. These simulations aim to reproduce a velocity shear layer on Mercury’s flanks, in the frame of the ESA/JAXA BEpiColombo mission. The magnetic field ratio between both side is fixed at B1/B2=0.5 for all simulations and the density ratio n1/n2 varies.