Lion roar emissions observed by the CLUSTER and THEMIS spacecraft

Lion roars are intense, narrow-band whistler-mode emissions sporadically occurring in the Earth's magnetosheath. We present a statistical study based on the CLUSTER data recorded during years 2001 and 2005. We have used the spectral analyzer STAFF-SA which is processing signals from three magnetic and two electric sensors. Frequency and power properties of lion roars have been investigated and generally correspond to previous results. We have also studied their spatial distribution. We have compared the field-aligned component of the Poynting flux and the local magnetic field in order to predict the source region. Our result shows that lion roars are mainly propagating toward the Earth. We thus expect that the source region is more often close to the bow shock. The SCM and EFI instruments on-board THEMIS provide measurements of all six components of the magnetic and electric field. It allows us to investigate properties of lion roar emissions. We present case studies of selected events.