We present a statistical study of the low (<1 Hz) frequency electric and magnetic field spectral densities observed by Cluster spacecraft in the high altitude cusp and mantle region. At the O<sup>+</sup> gyrofrequency (0.02–0.5 Hz) for this region the electric field spectral density is on average 0.2–2.2 (mV m<sup>−1</sup>)<sup>2</sup> Hz<sup>−1</sup>, implying that resonant heating at the gyrofrequency can be intense enough to explain the observed O<sup>+</sup> energies of 20–1400 eV. The relation between the electric and magnetic field spectral densities results in a large span of phase velocities, from a few hundred km s<sup>−1</sup> up to a few thousand km s<sup>−1</sup>. In spite of the large span of phase velocity, the ratio between the calculated local Alfvén velocity and the estimated phase velocity is close to unity. We provide average values of a coefficient describing diffusion in ion velocity space at different altitudes, which can be used in studies of ion energization and outflow. The observed average waves can explain the average O<sup>+</sup> energies measured in the high altitude (8–15 <I>R</I><sub>E</sub>) cusp/mantle region of the terrestrial magnetosphere according to our test particle calculations.