Waveform and packet structure of lion roars

The Equator-S magnetometer is very sensitive and has a sampling rate of nor mally 128 Hz. The high sampling rate allows for the first time fluxgate mag netometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of t he magnetic troughs of magnetosheath mirror waves, are near-monochromatic p ackets of electron whistler waves lasting for a few wave cycles only, typic ally 0.25 s. They are right-hand circularly polarized waves with typical am plitudes of 0.5-1 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is usually smaller than 1 .5 degrees.