shear or extremely steep positive shear, smaller than so-called the lower Liu limit or larger than the upper Liu limit, respectively [@Liu_etal06; @Priede11]. Although the transition between HMRI and SMRI is monotonic when decreasing the ratio of azimuthal to axial field [@Hollerbach_Ruediger05], the mathematics of this connection turned out to be quite subtle, including the formation of a spectral exceptional point where the original inertial mode coalesces with the slow magnetocoriolis mode [@Kirillov_Stefani10]. Moreover, the recent nonmodal analysis revealed a fundamental connection between the modal growth of HMRI and the nonmodal dynamics in the corresponding HD problem [@Mamatsashvili_Stefani16]. The relevance of HMRI for astrophysical Keplerian disks has also been considered: it seems to be a promising candidate to replace SMRI in weakly ionized parts of disks with small $Pm$, for example in the “dead zones” of protoplanetary disks or the outer parts of accretion disks around black holes. However, this issue is not yet fully resolved and under debate, because under standard conditions Keplerian shear alone might not be steep enough for HMRI to work [@Liu_etal06] unless other physical factors, such as specific electrical boundary conditions [@Ruediger_Hollerbach07; @Ruediger_Schultz08] or additional axial currents within the fluid are involved [@Kirillov_Stefani13].

The remarkable 