P.: Proton temperature anisotropy in the magnetosheath: comparison of 3-D MHD modelling with Cluster data

Abstract. We study four intervals of Cluster data, last-ing from five to eight hours, in the flanks of the magne-tosheath. In a first part, we make numerical simulations of these magnetosheath crossings, using a three-dimensional double-adiabatic MHD model of the magnetosheath and as-suming that the proton temperature anisotropy is bounded by the kinetic thresholds of the Alfvén proton cyclotron insta-bility and of the mirror instability. The conditions at the upstream boundary of the numerical domain are given by the solar wind parameters observed by ACE. We assume that the magnetopause is a fixed and impenetrable bound-ary, i.e. without magnetic reconnection. The global agree-ment between the observations and the simulations confirms the validity of the model in the magnetosheath flanks. We discuss the consequences of different models of the magne