Plot of the poloidal electric circuits at t_end for simulation K2. The two red curves are the critical surfaces, Alfvén (dotted) and FM (dashed). The yellow curves are the poloidal electric circuits, defined as isocontours of rB_ϕ, where the arrow indicate the direction of the poloidal current density J_p. Four circuits are highlighted in particular: (1) the envelope of the inner accelerating current in white (rB_ϕ = −2.06), (2) the outermost circuit still fully enclosed within the domain in blue (B_ϕ = −2.005), (3) a circuit closed outside the domain in orange (rB_ϕ = −1.80), and (4) a post-shock accelerating circuit in purple (also with rB_ϕ = −2.06).