Ribbon radius (top panel), eccentricity (middle panel) and semi-major axis rotation angle (bottom panel) for the simulation results (blue, green, and red dashed curves) and IBEX data (black solid curve). The rotation angle is defined as the counterclockwise angle between the semi-major axis of the fitted ellipse and 0° in azimuth (see Fig. 3). We also show the uncertainties of the results and data (except for IBEX rotation angle uncertainties), including the FWHM energy ranges of the IBEX-Hi energy passbands (McComas et al. 2012b), which are also used in the simulation.