Ranges of core and envelope magnetism for which a measurement of core magnetic field is considered accessible from the dip study, for model fz, represented as a dotted region in the {Le_core, Le_env} parameter space. The figure is coloured by the value of the envelope hydrodynamic spin parameter corresponding to the pure inertial mode, $s_{\mathrm{env}}^{*}$. The core and envelope Lehnert numbers are respectively related to the half-core magnetic field and to the magnetic field at the outer core-to-envelope boundary. Above the hatched line, the variation of the $s_{\mathrm{env}}^{*}$ is considered significantly deviating from its value in the solid-body, hydrodynamic case. To the right of the orange line, the hatched region shows the parameter space for which modes at $s_{\mathrm{env}}^{*}$ could be suppressed. The red continuous line shows the locus of equal Lehnert numbers in both zones. The white horizontal line shows an estimation of the magnetic field in the magnetostrophic regime obtained from the MESA model. The super-equipartition regime does not appear for the range of considered Le_core.