χ² maps of the EVE simulations. The maps are colored as a function of the difference between the projected minimum value of χ² along the other parameters in the plane temperature-mass loss and the overall minimum χ² corresponding to the best simulations (shown as black stars). The black line indicates the 3 σ level in both panels. Top panel: models with thermosphere only (see Section 6.3.2), the H/He ratio varied between 0.8 and 0.9. Bottom panel: models with thermosphere and exosphere (see Section 6.3.3), where the H/He ratio is fixed to 0.8.