Magnetospheric lion roars

The Equator-S magnetometer is very sensitive and has a sampling rate normal ly of 128 Hz. The high sampling rate for the first time allows detection of ELF waves between the ion cyclotron and the lower hybrid frequencies in th e equatorial dawnside magnetosphere. The characteristics of these waves are virtually identical to the lion roars typically seen at the bottom of the magnetic troughs of magnetosheath mirror waves. The magnetospheric lion roa rs are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.2 s. They are right-hand circularly polar ized waves with typical amplitudes of 0.5 nT at around one tenth of the ele ctron gyrofrequency. The cone angle between wave vector and ambient field i s nearly always smaller than 1 degrees.