Schematic of the different possible star–planet interactions, showing face-on views in the orbital plane of the four distinct morphological structures (denoted by the Latin numerals I, II, III, and IV) as they appear in the planet’s frame. The large and small solid disks (on the left and right sides of each panel) represent the star and the hot Jupiter, respectively, the shaded areas highlight material that flowed out of the planet, the arrows indicate gas motions, and the closed loops sketch the planetary magnetosphere. The solid circular arcs in panels I and IV have a radius R_m, the distance where the magnetospheric pressure equals the total ambient pressure, whereas the dashed circular arcs in panels II and III mark the distance R_w where the ambient pressure equals the ram pressure of the planetary wind. The dotted line indicates the contour of the effective (gravity plus centrifugal) potential that passes through the Lagrange point L₁ (at a distance R_t from the planet). The proposed classification scheme is based on the relative ordering of R_m, R_w, and R_t.