(a): Polarized white-light image of the corona recorded with the LASCO C2 on August 22, 2018. The inner boundary of the FOV is at 2 R_⊙ and the outer boundary is at about 6 R_⊙. The white circle indicates the limb of the solar disk. (b): Potential magnetic field extrapolated with PFSS model overlying on a photospheric synoptic magnetogram. The purple and green lines are representative of open field lines and the white lines are closed loops.