Reconstructed 2D magnetic field structures at core hydrogen mass fractions of X_c = 0.7 (left) and 0.1 (right), for our 1.5 M_⊙ model with an initial magnetic field strength of B_p, ini = 10 G and an initial rotation period of P_rot, ini = 1 d. The x-axis goes through the equatorial plane, while the z-axis corresponds to the stellar rotation axis. Thick purple lines show the stellar surface, while thin purple lines designate the convective core boundary. Green lines indicate magnetic field lines, the interval of which is taken such that 1 line in 1 R_⊙ corresponds to the field strength of 0.2 G. The field lines outside of the star are constructed assuming a dipole structure. The color indicates the strength of the toroidal field. Note that deformation due to centrifugal forces and structure change of the circumstellar magnetic field due to wind interaction are not taken into account here.