Minimal field strength required to account for the observed distortions in the g-mode period spacing for the 11 stars of our sample (black circles). They are plotted as a function of the mixed mode density , which is a proxy for evolution along the RGB (Gehan et al. 2018). The red dashed line indicates the critical field B_c and the gray long-dashed line shows the minimal field strength B_th required to detect the distortions in the g-mode pattern. The blue star symbols show the stars from Li et al. (2022).