Distribution of the horizontal Lorentz force at t = 0. Panel (a) shows the F_x distribution in horizontal slices z = 7.5 Mm in SES, in which F_x along x+ (x−) is plotted in green (plum). (c) F_x along the axis at t = 0 in SES, where the abscissa represents the y value of the sample point on the axis. Panels (b) and (d) are similar to panels (a) and (c), respectively, but for the FES case. Panels (a) and (b) focus on the center part of the simulation with (−60, 60) Mm in the x range and (−60, 60) Mm in the y range.