Properties of Mirror Mode Waves and Ion Cyclotron Waves Observed by Stereo

There are two instabilities that have the fastest growth rates in plasmas where Tperp>Tpar and beta>0: the ion cyclotron and the mirror mode instability. Downstream regions of interplanetary shocks such as the sheaths of Interplanetary Coronal Mass Ejections (ICMEs) and the leading edge of Stream Interaction Regions (SIRs) provide suitable conditions for the growth of both instabilities. We made a survey of mirror mode waves (MMWs) and ion cyclotron waves (ICWs) in the sheaths of ICMEs and inside SIRs observed by STEREO between 2007-2012. This study presents statistical results on the occurrence, characteristics and plasma conditions where these waves were observed. The MMWs were observed more frequently than the ICWs. The mirror mode is present as magnetic holes which occur isolated or in groups of holes. We also explore the shape and size of the mirror mode structures using the duration of the holes and their orientation with respect to the radial direction of the magnetic field. As for the ICWs, we found that these waves have similar characteristics to those studied by Jian et al. (2009 and 2010), in which the authors suggest a close-to-sun generation scenario. In this work we explore an in-situ generation possibility by using a dispersion solver using plasma parameters similar to those observed by STEREO. We give the range of plasma parameters under which the in-situ scenario could work and discuss the possibilities of both scenarios.