Abstract
Ion Cyclotron Waves (ICW) and Mirror Mode Waves (MMW) have been observed by the Cassini spacecraft in Saturn's middle magnetosphere (Russell et al. 2006; Leisner et al. 2006). These waves have a common origin since they require plasma temperature anisotropy (pressure) to grow (T_{⊥}/T_{∥}≫ 1). ICW have frequencies close to the gyro-frequencies of water group ions (Ω_{W^+}), they are left-handed and in most regions propagate at small angles to the ambient magnetic field (B_o). There are some regions where ICW have been observed with frequencies at twice the fundamental gyro-frequency and propagate at oblique angles. We interpret these waves as a Harmonic Mode Wave (HMW) (Rodríguez-Martínez et al. 2010). On the other hand, MMW are very compressive modes characterized by strong dips in B_o which are anti-correlated with the density.
