Self-polarization of the plasma element shortly after injection (ω_Lit = 0.6, where ω_Li is the ion Larmor frequency outside the magnetosphere) in the X_MSM = 1.96 R_M cross-section inside the simulation domain for case A: (top) total charge density and (middle) self-consistent electric field illustrated with vectors (the E_y component is color coded). The profiles of the charge density (blue) and E_y electric field (red) across Y_MSM (bottom). These profiles are averaged along the Z_MSM direction parallel to the magnetic field (shown with large purple arrows in the top and middle panels) from −0.11 R_M to +0.11 R_M. The white contour in the top and middle panels encloses the high-density core of the plasma element, while the yellow horizontal line in the bottom panel is drawn at E_y = −U₀B₀. The tall magenta boxes mark the two space charge layers of opposite polarity formed at the edges of the plasma element.