HMI brightening registered in flare kernels might be an artefact of the procedure, in which the HMI observables are produced. A careful investigation is needed by examining the individual filtergrams in detail.

![Reconstruction of the spectral-line shape using the HMI algorithm in case of the quiet Sun (top left: $I_{\rm c}=0.98$, $L_{\rm d}=0.55$) and in case the line-core has an emission contribution (top right: $I_{\rm c}=0.93$, $L_{\rm d}=0.30$), and an asymmetry (bottom: $I_{\rm c}=1.07$, $L_{\rm d}=0.51$). The solid line represents the reference “quiet-Sun” spectral-line model, the points then the synthetic intensities obtained by applying the six idealised HMI band-pass filters to the modelled line profile, and the dashed line represents the reconstruction of the spectral-line shape from the six points. []{data-label="fig:spline"}](line_profile_norm.pdf "fig:"){width="49.00000%"} ![Reconstruction of the spectral-line shape using the HMI algorithm in case of the quiet Sun (top left: $I_{\rm c}=0.98$, $L_{\rm d}=0.55$) and in case the line-core has an emission contribution (top right: $I_{\rm c}=0.93$, $L_{\rm d}=0.30$), and an asymmetry (bottom: $I_{\rm c}=1.07$, $L_{\rm d}=0.51$). The solid line represents the reference “quiet-Sun” spectral-line model, the points then the synthetic intensities obtained by applying the six idealised HMI band-pass filters to the modelled line profile, and the dashed line represents 