**4. Conclusions**

We considered the ultramagnetized atomic nuclei which arise in explosions of type II supernovae, neutron star mergers, during collisions of heavy ions, and in magnetar crusts. It is shown that for a field strength of 0.1—10 TT, the magnetic response of nucleons is determined by the Zeeman effect. Accordingly, dominant linear magnetic susceptibility is represented as the combined reactivity of valent nucleons and binding energy increases for open-shell nuclei. For magic nuclei with closed shells, the binding energy is effectively reduced due to the field-induced additional pressure in a free nucleon gas. As a result, the composition of atomic nuclei formed in an ultramagnetized plasma depends on the field strength. Considerable magnetic modification of nuclear properties is predicted for mass numbers corresponding to large valent shell spins and pronounced magic numbers, i.e., N&Z = 28, 50, 82, 126 ...

The magnetic structure change for 1 *f*7/2 shell nuclei (iron group) enhances nucleosynthesis products of smaller mass numbers. In particular, an increase in the volume part of the titanium 44Ti isotope at a field induction of several TT is in satisfactory agreemen<sup>t</sup> with data of direct observations of SN remnants [2,6,8,9]. Such an induction of the magnetic field is consistent with SN explosion energy [2]. These conditions of nucleosynthesis imply a significant increase in a portion of the main titanium isotope,48Ti, in the chemical composition of galaxies.

As an example of the synthesis of nuclei with open <sup>1</sup>*g*9/2 shell and magic number *N* = 50, we see that magnetic effects in the r-process give rise to an enrichment of nuclear components with smaller mass numbers as well. However, a large volume of isotones with *N* = 50 remains robust. Then, a magnetic effect in the r-process peak is expected to result in some enhancement of volume of small mass number nuclides. The magnetic effects considered can also stimulate dynamical deformations in nuclear collisions which are important in subbarrier fusion reactions [18,19] and in the formation, composition, structure, and topology of magnetar inner crusts, see [20].

We notice, finally, that heavy ion collisions giving rise to magnetic fields of ~10<sup>2</sup> TT affect quark and gluon dynamics [4], with potential effects on the chiral transition and quarkyonic matter [21] which are important in the experiments being undertaken at the Facility for Antiproton and Ion Research (FAIR) at GSI and the Nuclotron-based Ion Collider fAcility (NICA) at JINR.

**Funding:** This research received no external funding.

**Acknowledgments:** Author (V.N.K.) thanks JINR (Dubna) for the warm hospitality and the financial support.

**Conflicts of Interest:** The authors declare no conflict of interest.
