Relationships between S and B_max of MC. Panel a1, a2, a3, a4: number density of MCs in B_max and S space in different solar-cycle phases. The contour lines correspond to 3, 15, 30, 150, 300, and 450 MCs. The black line shows the square-root fit. Panel a5: square-root fit coefficient α versus sunspot number. The blue dashed line shows sunspot numbers. The Φ of MCs in panels b1, b2, b3, b4, and b5 is less than 5.5 × 10¹⁸ Mx.