Fig. 1: Key features in the L_x = 2.5d_i case and reconnection rates.

a Electron outflow speed V_ex overlaid with the contour of the in-plane magnetic flux ψ. Note that the entire domain is smaller than the typical ion diffusion region (IDR) in standard reconnection. b Ion outflow speed V_ix overlaid with the separatrices in dashed black. The red box of size 2L_e × 2δ_e marks the electron diffusion region (EDR). The corners (such as point “6”) of the green box of size 2L₀ × 2δ₀ mark the locations downstream of which the exhaust opening angle quickly decreases to 0. c Cuts of V_ex, V_ix and the E × B drift speed along the z = 0 line. The (red and green) dashed vertical lines mark the outflow boundaries of the EDR and the green box in (b), while the magenta dashed horizontal line denotes the limiting speed. d In blue the electron Alfvén speed based on the local B_x and n_e as a function of z at x = 0. In gray the electron inflow speed V_ez × 20. In green the electron density n_e × 43. In purple the peak velocity V_ex,peak from (c). The red shaded band marks the EDR. e Reconnection rate R as a function of time for simulations of different system sizes. The rates in our simulations are computed from R = (∂Δψ/∂t)/B_x0V_Ai0 where Δψ is the magnetic flux difference between the X-line and the O-line. Note that ∂Δψ/∂t = cE_R, the reconection electric field, in 2D systems. The gray dashed horizontal line indicates the typical rate of ion-coupled standard reconnection³¹. The transparent color circles mark the time of these V_ex contours in Fig. 2.