Cluster observations of structures at quasi-parallel bow shocks, Ann

Part of Special Issue “Spatio-temporal analysis and multipoint measurements in space” Abstract. Collisionless quasi-parallel shocks are thought to be composed of a patchwork of short, large-amplitude magnetic structures (SLAMS) which act to thermalise the plasma, giving rise to a spatially extended and time vary-ing shock transition. With the launch of Cluster, new ob-servations of the three-dimensional shape and size of shock structures are available. In this paper we present SLAMS observations made when the Cluster tetrahedron scale size was ∼100 km. The SLAMS magnetic field enhancement is typically well correlated between spacecraft on this scale, al-though small differences are observed. The statistical charac-teristics of these differences contain information on the typ-ical gradients of magnetic field changes within the SLAM structure which, in the case studied here, occur on scales of 100–150 km, comparable with the upstream ion inertial length. Key words. Interplanetary physics (planetary bow shocks; plasma waves and turbulence)