Crustal field effect on the magnetic field topology in the southern hemisphere of the X–Z plane in the MSO coordinates under the southward IMF (B_Z = −3 nT). In panels a–f, the subsolar location of Mars is fixed to the 0° north latitude when the west longitude is 0°, 45°, 90°, 120°, 150°, and 180°, respectively. The black lines with arrows represent the magnetic field lines, and the color bars show the solar wind thermal pressure. The locations of the Martian MPB (the red dots) are identified by the same method of Fig. 3; the red lines are the MPB model results of Vignes et al. (2000).