Well I must admit, when it comes to magnets I haven't a clue. I know that Mars has no magnetosphere and it's why it has such a thin atmosphere. The earth's magnetosphere, if I understand right, is not very strong, but the earth is a rather large magnet, so it's affect on solar wind extends far out into space. The surface of Mars is abundant with Iron (III) Oxide, which exhibits paramagnetism (atoms align in an externally applied magnetic field, amplifying the overall strength of the magnetic field). Could we not strategically place very strong magnets over the surface of Mars and take advantage of paramagnetic effects to give Mars and magnetosphere?