Sketch explaining the transformation of the VDF and relative V_αp at the magnetic field line kinks of the switchbacks. The central diagram shows the magnetic line configuration containing three sections: “F” (top) in the fastest plasma stream, “S” (bottom) in the slowest plasma stream, and “I” the magnetic field section connecting the “F” and “S” sections via two kinks. The blue dot under the “I” field line represents the spacecraft motion in the plasma frame of reference. The left and right diagrams show corresponding VDFs in the kink frame. The vertical solid line in the distribution shows the kink velocity (i.e. the deHoffman-Teller frame). The small dashed vertical lines in the distributions show the plasma bulk velocity in the kink frame. The green filled dashed contour shows the original proton distribution in sections “F” or “S”, and the small dark green solid circle is the α-particles bulk velocity. The blue filled contour and the dark blue circle are the part of the original VDF after the transformation at the kink.