Schematic view in the R − T plane of the evolution of the FR (size, direction, and parameters) from the BepiColombo to Solar Orbiter location. The FR rotated from the N direction into the R − T plane (see text for details). We note that R_FR is radius of the FR, B_core is core field of the FR, v_FR is travel speed of the FR, and is the axial direction of the FR in RTN coordinates.