Multi-spacecraft study of foreshock cavitons with Cluster

We use the data of the four Cluster probes in order to search for and study the time evolution of foreshock cavitons. The data were obtained during April and May 2016 when the four Cluster spacecraft were aligned along the Sun-Earth line. This configuration was proposed in two research projects that were selected in the frame of the ESÁs Cluster Guest Investigator Programme. We first analyzed the data in order to determine the periods when Cluster was in different regions of space (pristine solar wind, foreshock region, magnetosheath and magnetosphere). We then looked for the caviton signatures in the foreshock - simultaneous drops in the magnetic field magnitude and plasma density surrounded by the rims in which these values are enhanced compared to the ambient values. In total we found 33 foreshock cavitons of which only 17 were observed with only one spacecraft, 10 were observed by two spacecraft and 6 were observed by three probes. Here we present the most events and discuss their observational properties.