Panel a: energy gains by the escaping electrons (measured when they leave the first trapped island) vs. the guiding field magnitude: ξ_y = 0.0, 10⁻⁴, 10⁻², 0.1, 0.6, 1.0. The other parameters are: E_y0 = 100 V m⁻¹, B_z0 = 100G, ϵ = 0.3, d = 2 m, k = 0.03125. Panel b: energy gains by the escaping electrons vs. the half length of the islands: L_i = 2 m, 6.4 m, 20 m, 64 m. Panel c: fluctuation of B_x on the x = 0 m plane for different aspect ratios L_i/d (k⁻¹). Panel d: corresponding fluctuation of E_y on the x = 0 plane. The other parameters are: E_y0 = 100 V m⁻¹, B_z0 = 100G, ξ_y = 1.0, ϵ = 0.3, d = 2 m.