Top two panels: magnetic field model of the active region on 1 April and 4 April overlaid on AIA 193 Å images with the intensity reversed. Bottom two panels: same model, but overlaid on the Doppler velocity maps with blue showing blue shifts and red showing red shifts (the colour range is +/−20 km s⁻¹). The AR expands as it evolves. At its edges on 1 April, we observe structures in AIA data that are closed within theAR. On 4 April, the magnetic field lines derived from our model look more expanded at the edges of the AR, and larger scale magnetic field lines are relevant in correspondence with the blue-shifted region. The axes in all panels are labelled in Megametres, with the origin set in the AR centre (located at N12E31on 1 April and at N13W05 on 4 April). The iso-contours of the line-of-sight field correspond to ±50, ±100, and ±500 G in continuous magenta (blue) style for the positive (negative) values. Sets of computed field lines matching the global shape of theobserved coronal loops in the AIA 193 Å images were added in a continuous line and red colour in the two top panels and repeated in the two bottom panels.