On the 3D global dynamics of terrestrial bow-shock rippling in a quasi-perpendicular interaction with steady solar wind
Résumé
The phenomenon of bow-shock surface rippling has been studied throughout multidimensional simulations of ad hoc planar shock fronts. However, the investigation of global bow-shock behaviour with a 3D curved scenario has been poorly addressed thus far. In this work, we present an analysis of this scenario occurring during a low-β quasiperpendicular interaction with the interplanetary magnetic field by means of kinetic 3D computer simulations. The analysis was carried out with 3D hybrid simulations properly set to reproduce the interaction between solar wind and a realistic near-Earth environment. We have found that the ripples behave as IMFperpendicular elongated structures extending along the bow-shock meridian plane and propagating parallel to the IMF orientation from the nose towards the flanks with a constant velocity (in the case studied here ∼ 8 times the upstream Alfvén speed). We have also confirmed that these ripples feature a broad range of wavelengths along the entire travel path, as locally observed with past simulations and observations (in this case ≥ 8 d i). Moreover, from a kinetic analysis of the velocity distribution across the bow-shock nose, we have observed global signatures of the occurrence of shock-front reformation. We suggest that, among other kinetic mechanisms, shock-front reformation in the nose region can play an important role in the perturbation of the bow-shock surface, leading to the generation of modulations ultimately propagating along the bow-shock surface as MHD waves.
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