Magnetic Structure around a Neutron Star Inferred from Quasi-Periodic Oscillations in Low Mass X-Ray Binaries

The recently suggested Two-Oscillator model for quasi-periodic oscillations (QPO) allows us to reconstruct the profile of rotational frequency in the disk surrounding the neutron star in a binary system. The differential rotation in a highly conductive plasma is dependent on the magnetic structure of the star. Interpreting QPO, we found the relative contribution of magnetic multipoles in the makeup of the neutron star and its magnetosphere. We draw our conclusions from the close analogy between the Sun and a neutron star which both, in general, can be treated as non-aligned magnetic rotators. In our review, the north-south asymmetry due to the magnetic quadrupole (Osherovich, Tzur and Gliner, 1984), the current sheet close to the equatorial plane and the polar regions with open field lines will be discussed as common features for both stars.