The role of the mass of the solar wind positive charged ions. The figure shows the total magnetic field on the noon-midnight meridian plane, y = 0, in (a) a realistic situation, where the mass of the solar wind protons are mp and (b) in a test case, when the mass of the solar wind positively charged ions was reduced to 1/3 × mp. In both runs the bulk velocity, the Alfvén velocity and the thermal velocity of the solar wind are similar. The spherical shell is 3600 km (~1.06 Rm) from the center of the Mars and the color on its surface shows the total magnetic field. In both runs the solution is symmetric on the dawn-dusk plane, z = 0, between the y > 0 and y < 0 hemispheres (figures not shown). The unit of the axes is the radius of Mars.