Dependence of the magnetopause Kelvin‐Helmholtz instability on the orientation of the magnetosheath magnetic field

It is shown by means of a 2‐D MHD simulation that the observed rotation of the unperturbed magnetic field within the magnetopause (MP), which is assumed to be a tangential discontinuity (TD), leads to a significant dependence of the magnetopause Kelvin‐Helmholtz (K‐H) instability on the orientation of the sheath field. That is, northward sheath B z is more favorable to the instability than southward B z and the MP undulates most strongly when the sheath field points due north. When the sheath field does not point due north, a slow rarefaction region is formed in the velocity boundary layer (BL) inside the MP, wherein there are minima of the plasma pressure and temperature accompanied by a maximum of the magnetic pressure.