  Cataclysmic variables (CVs) are interacting binary systems where a cool,
rapidly rotating secondary star passes material to a white dwarf. If this mass
loss is to continue then there must be continuous angular momentum loss from
the system. By analogy with the Sun and other cool stars, it has been assumed
that magnetic braking is responsible, angular momentum being carried away by an
ionised wind from the secondary star, threading a dynamo-generated magnetic
field. We have discovered TiO absorption in the spectrum of SS Cyg, whose
secondary star should be too hot to show such features. The most likely
explanation of its presence is cool star spots caused by the strong (0.1T)
fields required by the magnetic braking theories.
