Top left: Hα profiles of ρ Oph Ab at maximum emission (red) and minimum emission (blue), shown with a synthetic spectrum (thick green). Bottom left: residual flux after subtracting the synthetic spectrum from the observed spectra. Horizontal green line indicate the continuum level. Vertical dashed and dot-dashed lines show ±υ sin i and the velocities corresponding to ±R_K, respectively (since the magnetosphere cororates with the star, there is a direct linear relationship between line-of-sight velocity and projected distance). Right panels: equivalent widths measured from (bottom to top) the blue wing, the line core, the red wing, and the combined blue and red EWs. Dashed and dotted vertical lines show 〈B_z〉 extrema and nulls from the fit in Fig. 9. Horizontal thick green lines show the continuum level. Curves show harmomic fits.