In this study we use two-loop model SCW (SCW2L) to quantitatively investigate distortion of the ionospheric footpoint pattern in response to changes of different SCW2L parameters. Calculation results show that SCW-related footprint shifts result in formation of auroral bulge and westward travelling surge and may contribute to rotation of auroral streamers, and that SCW2L combined with the AM03 model nicely describes the azimuthal progression and the observed magnitude of the auroral expansion.