Comparison between the full isotropic model (panel a), and the hybrid model (panel b). In both cases, the red contours correspond to the models and the black ones to the observations. The observation date is March 14, 2017. For modelling purposes, the image was rebinned ×2 with respect to the value given in Table 1. Therefore, the resolution is 612.6 km pixel⁻¹. In all cases the isophote levels are: 4 × 10⁻¹⁴, 7 × 10⁻¹⁴, 1.25 × 10⁻¹³ and 4 × 10⁻¹³ SDU. The validity of the models, determined via the χ parameter, confirms that the isotropic model offers a poorer fit (χ_isotropic = 3.9) than the hybrid model (χ_hybrid = 2.4). The plot is orientated so that north is up and east is to the left.