The results without poloidal field at t = 10⁴H_b/c_b. a) The contour of toroidal magnetic field (log  [(B_y/B₀)²] ). b) The vorticity of y-direction in the white rectangle in panel a normalized by c_b/H_b. The point where vorticity has a maximum value is indicated with an asterisk. This point is defined as the origin of a circular geometry in order to calculate angular velocity and angular momentum. c) The angular velocity normalized by c_b/H_b. d) The angular momentum normalized by ρ_bH_bc_b.