ULF waves are present in the magnetic records returned by the Mariner 10 spacecraft. An analysis of samples of these data show that near the magnetopause the waves are right-hand circularly polarized and about 3 nT in amplitude. These waves weaken and become linearly polarized as the spacecraft moves inward. Deep in the magnetosphere narrowband waves with 2-second periods are found. These waves may be standing waves on field lines anchored in the core. ¿ American Geophysical Union 1989